diff --git a/package.xml b/package.xml
index a66c5b6256..739f44e648 100644
--- a/package.xml
+++ b/package.xml
@@ -466,6 +466,7 @@ http://pear.php.net/dtd/package-2.0.xsd">
         <file baseinstalldir="PHP/CodeSniffer" name="ForLoopShouldBeWhileLoopSniff.php" role="php" />
         <file baseinstalldir="PHP/CodeSniffer" name="ForLoopWithTestFunctionCallSniff.php" role="php" />
         <file baseinstalldir="PHP/CodeSniffer" name="JumbledIncrementerSniff.php" role="php" />
+        <file baseinstalldir="PHP/CodeSniffer" name="MixedBooleanOperatorSniff.php" role="php" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnconditionalIfStatementSniff.php" role="php" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnnecessaryFinalModifierSniff.php" role="php" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnusedFunctionParameterSniff.php" role="php" />
@@ -602,6 +603,8 @@ http://pear.php.net/dtd/package-2.0.xsd">
         <file baseinstalldir="PHP/CodeSniffer" name="ForLoopWithTestFunctionCallUnitTest.php" role="test" />
         <file baseinstalldir="PHP/CodeSniffer" name="JumbledIncrementerUnitTest.inc" role="test" />
         <file baseinstalldir="PHP/CodeSniffer" name="JumbledIncrementerUnitTest.php" role="test" />
+        <file baseinstalldir="PHP/CodeSniffer" name="MixedBooleanOperatorUnitTest.inc" role="test" />
+        <file baseinstalldir="PHP/CodeSniffer" name="MixedBooleanOperatorUnitTest.php" role="test" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnconditionalIfStatementUnitTest.inc" role="test" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnconditionalIfStatementUnitTest.php" role="test" />
         <file baseinstalldir="PHP/CodeSniffer" name="UnnecessaryFinalModifierUnitTest.inc" role="test" />
diff --git a/src/Standards/Generic/Sniffs/CodeAnalysis/MixedBooleanOperatorSniff.php b/src/Standards/Generic/Sniffs/CodeAnalysis/MixedBooleanOperatorSniff.php
new file mode 100644
index 0000000000..6e3a070147
--- /dev/null
+++ b/src/Standards/Generic/Sniffs/CodeAnalysis/MixedBooleanOperatorSniff.php
@@ -0,0 +1,116 @@
+<?php
+/**
+ * Forbid mixing different binary boolean operators within a single expression without making precedence
+ * clear using parentheses.
+ *
+ * <code>
+ * $one = false;
+ * $two = false;
+ * $three = true;
+ *
+ * $result = $one && $two || $three;
+ *
+ * $result3 = $one && !$two xor $three;
+ *
+ *
+ * if (
+ *     $result && !$result3
+ *     || !$result && $result3
+ * ) {}
+ * </code>
+ *
+ * @author    Tim Duesterhus <duesterhus@woltlab.com>
+ * @copyright 2021 WoltLab GmbH.
+ * @license   https://github.com/squizlabs/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Standards\Generic\Sniffs\CodeAnalysis;
+
+use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\Sniff;
+use PHP_CodeSniffer\Util\Tokens;
+
+class MixedBooleanOperatorSniff implements Sniff
+{
+
+    /**
+     * Array of tokens this test searches for to find either a boolean
+     * operator or the start of the current (sub-)expression. Used for
+     * performance optimization purposes.
+     *
+     * @var array<int|string>
+     */
+    private $searchTargets = [];
+
+
+    /**
+     * Returns an array of tokens this test wants to listen for.
+     *
+     * @return array<int|string>
+     */
+    public function register()
+    {
+        $this->searchTargets  = Tokens::$booleanOperators;
+        $this->searchTargets += Tokens::$blockOpeners;
+        $this->searchTargets[\T_INLINE_THEN] = \T_INLINE_THEN;
+        $this->searchTargets[\T_INLINE_ELSE] = \T_INLINE_ELSE;
+
+        return Tokens::$booleanOperators;
+
+    }//end register()
+
+
+    /**
+     * Processes this test, when one of its tokens is encountered.
+     *
+     * @param \PHP_CodeSniffer\Files\File $phpcsFile The file being scanned.
+     * @param int                         $stackPtr  The position of the current token
+     *                                               in the stack passed in $tokens.
+     *
+     * @return void
+     */
+    public function process(File $phpcsFile, $stackPtr)
+    {
+        $tokens = $phpcsFile->getTokens();
+
+        $start = $phpcsFile->findStartOfStatement($stackPtr);
+
+        $previous = $phpcsFile->findPrevious(
+            $this->searchTargets,
+            ($stackPtr - 1),
+            $start,
+            false,
+            null,
+            true
+        );
+
+        if ($previous === false) {
+            // No token found.
+            return;
+        }
+
+        if ($tokens[$previous]['code'] === $tokens[$stackPtr]['code']) {
+            // Identical operator found.
+            return;
+        }
+
+        if (\in_array($tokens[$previous]['code'], [\T_INLINE_THEN, \T_INLINE_ELSE], true) === true) {
+            // Beginning of the expression found for the ternary conditional operator.
+            return;
+        }
+
+        if (isset(Tokens::$blockOpeners[$tokens[$previous]['code']]) === true) {
+            // Beginning of the expression found for a block opener. Needed to
+            // correctly handle match arms.
+            return;
+        }
+
+        // We found a mismatching operator, thus we must report the error.
+        $error  = 'Mixing different binary boolean operators within an expression';
+        $error .= ' without using parentheses to clarify precedence is not allowed.';
+        $phpcsFile->addError($error, $stackPtr, 'MissingParentheses');
+
+    }//end process()
+
+
+}//end class
diff --git a/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.inc b/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.inc
new file mode 100644
index 0000000000..f46ab9081f
--- /dev/null
+++ b/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.inc
@@ -0,0 +1,131 @@
+<?php
+
+if (true && true || true); // Not OK.
+if ((true && true) || true);
+if (true && (true || true));
+
+$var = true && true || true; // Not OK.
+$var = (true && true) || true;
+$var = true && (true || true);
+
+$complex = true && (true || true) && true;
+$complex = true && (true || true) || true; // Not OK.
+
+if (
+    true
+    && true
+    || true // Not OK.
+);
+
+if (
+    true
+    && (
+        true
+        || true
+    )
+);
+
+if (true && foo(true || true));
+if (true && foo(true && true || true)); // Not OK.
+if (true && $foo[true || true]);
+if (true && $foo[true && true || true]); // Not OK.
+
+if (true && foo(true) || true); // Not OK.
+if (true && $foo[true] || true); // Not OK.
+if (true && foo($foo[true]) || true); // Not OK.
+
+$foo[] = true && true || false; // Not OK.
+
+foo([true && true || false]); // Not OK.
+
+if (true && true || true && true); // Not OK.
+
+$foo = false || true && (#[\Attr(true && true || true)] function (#[\SensitiveParameter] $p) { // Not OK.
+    echo true || true && true; // Not OK.
+
+    return true;
+})('dummy') || false; // Not OK.
+
+$foo = false || (true && (#[\Attr((true && true) || true)] function (#[\SensitiveParameter] $p) {
+    echo (true || true) && true;
+
+    return true;
+})('dummy')) || false;
+
+$foo = true || true || (#[\Attr(true && true && true)] function (#[\SensitiveParameter] $p) {
+    echo true && true && true;
+
+    return true;
+})('dummy') || false;
+
+if (true && [true, callMe(), ${true || true}] || true); // Not OK.
+if (true && [true, callMe(), ${true || true}] && true);
+
+for (true || true || true; true && true && true; true || true || true);
+for (true || true && true; true && true || true; true || true && true); // Not OK.
+
+for ($a = true || true || true, $b = true && true && true; $a; $b);
+for ($a = true || true && true, $b = true || true && true; $a; $b); // Not OK.
+
+$foo = true || true || true ? true && true && true : true || true || true;
+$foo = true && true || true // Not OK.
+    ? true || true && true // Not OK.
+    : true || true && true; // Not OK.
+
+for(true || true || true, true && true && true);
+for(true && true || true, true && true || true); // Not OK.
+
+(true && true and true); // Not OK.
+(true && true or true); // Not OK.
+(true and true or true); // Not OK.
+(true and true xor true and true); // Not OK.
+
+if (true || true && true && true && true); // Not OK.
+
+match (true) {
+    // OK.
+    $a || ($b && $c) => true,
+};
+
+match (true) {
+    // Not OK.
+    $a || $b && $c => true,
+};
+
+match (true) {
+    // OK.
+    $a || $b => true,
+    $a && $b => true,
+};
+
+match (true) {
+    // Debatable.
+    $a || $b, $a && $b => true,
+};
+
+// OK.
+$foo = fn ($a, $b, $c) => $a && ($b || $c);
+
+// Not OK.
+$foo = fn ($a, $b, $c) => $a && $b || $c;
+
+// OK.
+$foo = $a && (fn ($a, $b, $c) => $a || $b);
+
+// Debatable.
+$foo = $a && fn ($a, $b, $c) => $a || $b;
+
+// OK.
+\array_map(
+    fn ($a, $b, $c) => $a || $b,
+    $a && $b
+);
+
+match (true) {
+    // Not OK.
+    $a || ($b && $c) && $d => true,
+    // Not OK.
+    $b && $c['a'] || $d => true,
+    // Not OK.
+    $b && ${$var} || $d => true,
+};
diff --git a/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.php b/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.php
new file mode 100644
index 0000000000..74a0b7530a
--- /dev/null
+++ b/src/Standards/Generic/Tests/CodeAnalysis/MixedBooleanOperatorUnitTest.php
@@ -0,0 +1,85 @@
+<?php
+/**
+ * Unit test class for the MixedBooleanOperator sniff.
+ *
+ * @author    Tim Duesterhus <duesterhus@woltlab.com>
+ * @copyright 2021 WoltLab GmbH.
+ * @license   https://github.com/squizlabs/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Standards\Generic\Tests\CodeAnalysis;
+
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+
+class MixedBooleanOperatorUnitTest extends AbstractSniffUnitTest
+{
+
+
+    /**
+     * Returns the lines where errors should occur.
+     *
+     * The key of the array should represent the line number and the value
+     * should represent the number of errors that should occur on that line.
+     *
+     * @return array<int, int>
+     */
+    public function getErrorList()
+    {
+        return [
+            3   => 1,
+            7   => 1,
+            12  => 1,
+            17  => 1,
+            29  => 1,
+            31  => 1,
+            33  => 1,
+            34  => 1,
+            35  => 1,
+            37  => 1,
+            39  => 1,
+            41  => 2,
+            43  => 2,
+            44  => 1,
+            47  => 1,
+            61  => 1,
+            65  => 3,
+            68  => 2,
+            71  => 1,
+            72  => 1,
+            73  => 1,
+            76  => 2,
+            78  => 1,
+            79  => 1,
+            80  => 1,
+            81  => 2,
+            83  => 1,
+            92  => 1,
+            110 => 1,
+            126 => 1,
+            128 => 1,
+            130 => 1,
+
+            // Debatable.
+            103 => 1,
+            116 => 1,
+        ];
+
+    }//end getErrorList()
+
+
+    /**
+     * Returns the lines where warnings should occur.
+     *
+     * The key of the array should represent the line number and the value
+     * should represent the number of warnings that should occur on that line.
+     *
+     * @return array<int, int>
+     */
+    public function getWarningList()
+    {
+        return [];
+
+    }//end getWarningList()
+
+
+}//end class