diff --git a/src/connection_string.ts b/src/connection_string.ts
index 5b3da011ed4..bac2a13207f 100644
--- a/src/connection_string.ts
+++ b/src/connection_string.ts
@@ -33,7 +33,6 @@ import type { TagSet } from './sdam/server_description';
 import {
   DEFAULT_PK_FACTORY,
   emitWarning,
-  emitWarningOnce,
   HostAddress,
   isRecord,
   matchesParentDomain,
@@ -162,29 +161,16 @@ function checkTLSOptions(allOptions: CaseInsensitiveMap): void {
   check('tlsAllowInvalidCertificates', 'tlsDisableOCSPEndpointCheck');
   check('tlsDisableCertificateRevocationCheck', 'tlsDisableOCSPEndpointCheck');
 }
-
-const TRUTHS = new Set(['true', 't', '1', 'y', 'yes']);
-const FALSEHOODS = new Set(['false', 'f', '0', 'n', 'no', '-1']);
 function getBoolean(name: string, value: unknown): boolean {
   if (typeof value === 'boolean') return value;
-  const valueString = String(value).toLowerCase();
-  if (TRUTHS.has(valueString)) {
-    if (valueString !== 'true') {
-      emitWarningOnce(
-        `deprecated value for ${name} : ${valueString} - please update to ${name} : true instead`
-      );
-    }
-    return true;
-  }
-  if (FALSEHOODS.has(valueString)) {
-    if (valueString !== 'false') {
-      emitWarningOnce(
-        `deprecated value for ${name} : ${valueString} - please update to ${name} : false instead`
-      );
-    }
-    return false;
+  switch (value) {
+    case 'true':
+      return true;
+    case 'false':
+      return false;
+    default:
+      throw new MongoParseError(`${name} must be either "true" or "false"`);
   }
-  throw new MongoParseError(`Expected ${name} to be stringified boolean value, got: ${value}`);
 }
 
 function getIntFromOptions(name: string, value: unknown): number {
diff --git a/test/unit/assorted/uri_options.spec.test.ts b/test/unit/assorted/uri_options.spec.test.ts
index 8420ff38709..f6ac356df9f 100644
--- a/test/unit/assorted/uri_options.spec.test.ts
+++ b/test/unit/assorted/uri_options.spec.test.ts
@@ -14,16 +14,18 @@ describe('URI option spec tests', function () {
     'tlsDisableCertificateRevocationCheck can be set to true',
     'tlsDisableCertificateRevocationCheck can be set to false',
     'tlsDisableOCSPEndpointCheck can be set to true',
-    'tlsDisableOCSPEndpointCheck can be set to false'
+    'tlsDisableOCSPEndpointCheck can be set to false',
+
+    // NOTE(NODE-3989): Skipped because we now only accept true/false for boolean options. The spec expects us to
+    // warn on other accepted but deprecated values, but as of NODE-3989, we now throw on these
+    // values
+    'Invalid loadBalanced value'
   ];
 
   const testsThatDoNotThrowOnWarn = [
     // TODO(NODE-3923): compression option validation
     'Too high zlibCompressionLevel causes a warning',
-    'Too low zlibCompressionLevel causes a warning',
-
-    // TODO(NODE-3989): Fix legacy boolean parsing
-    'Invalid loadBalanced value'
+    'Too low zlibCompressionLevel causes a warning'
   ];
 
   for (const suite of suites) {
diff --git a/test/unit/connection_string.test.ts b/test/unit/connection_string.test.ts
index 54c4733aa2f..98866db767e 100644
--- a/test/unit/connection_string.test.ts
+++ b/test/unit/connection_string.test.ts
@@ -211,13 +211,38 @@ describe('Connection String', function () {
     });
   });
 
-  it('should parse boolean values', function () {
-    let options = parseOptions('mongodb://hostname?retryWrites=1');
-    expect(options.retryWrites).to.equal(true);
-    options = parseOptions('mongodb://hostname?retryWrites=false');
-    expect(options.retryWrites).to.equal(false);
-    options = parseOptions('mongodb://hostname?retryWrites=t');
-    expect(options.retryWrites).to.equal(true);
+  context('boolean options', function () {
+    const valuesExpectations: { value: string; expectation: 'error' | boolean }[] = [
+      { value: 'true', expectation: true },
+      { value: 'false', expectation: false },
+      { value: '-1', expectation: 'error' },
+      { value: '1', expectation: 'error' },
+      { value: '0', expectation: 'error' },
+      { value: 't', expectation: 'error' },
+      { value: 'f', expectation: 'error' },
+      { value: 'n', expectation: 'error' },
+      { value: 'y', expectation: 'error' },
+      { value: 'yes', expectation: 'error' },
+      { value: 'no', expectation: 'error' },
+      { value: 'unknown', expectation: 'error' }
+    ];
+    for (const { value, expectation } of valuesExpectations) {
+      const connString = `mongodb://hostname?retryWrites=${value}`;
+      context(`when provided '${value}'`, function () {
+        if (expectation === 'error') {
+          it('throws MongoParseError', function () {
+            expect(() => {
+              parseOptions(connString);
+            }).to.throw(MongoParseError);
+          });
+        } else {
+          it(`parses as ${expectation}`, function () {
+            const options = parseOptions(connString);
+            expect(options).to.have.property('retryWrites', expectation);
+          });
+        }
+      });
+    }
   });
 
   it('should parse compression options', function () {