diff --git a/crates/ruff_linter/resources/test/fixtures/ruff/RUF065_1.py b/crates/ruff_linter/resources/test/fixtures/ruff/RUF065_1.py
index 048a5be48c..c5071f8ac7 100644
--- a/crates/ruff_linter/resources/test/fixtures/ruff/RUF065_1.py
+++ b/crates/ruff_linter/resources/test/fixtures/ruff/RUF065_1.py
@@ -16,3 +16,19 @@ logging.warning("%s", str(**{"object": b"\xf0\x9f\x9a\xa8", "encoding": "utf-8"}
 # str() with single keyword argument - should be flagged (equivalent to str("!"))
 logging.warning("%s", str(object="!"))
 
+
+# Complex conversion specifiers that make oct() and hex() necessary
+# These should NOT be flagged because the behavior differs between %s and %#o/%#x
+# https://github.com/astral-sh/ruff/issues/21458
+
+# %06s with oct() - zero-pad flag with width (should NOT be flagged)
+logging.warning("%06s", oct(123))
+
+# % s with oct() - blank sign flag (should NOT be flagged)
+logging.warning("% s", oct(123))
+
+# %+s with oct() - sign char flag (should NOT be flagged)
+logging.warning("%+s", oct(123))
+
+# %.3s with hex() - precision (should NOT be flagged)
+logging.warning("%.3s", hex(123))
diff --git a/crates/ruff_linter/src/rules/ruff/rules/logging_eager_conversion.rs b/crates/ruff_linter/src/rules/ruff/rules/logging_eager_conversion.rs
index 32c4755229..920f6c73a5 100644
--- a/crates/ruff_linter/src/rules/ruff/rules/logging_eager_conversion.rs
+++ b/crates/ruff_linter/src/rules/ruff/rules/logging_eager_conversion.rs
@@ -2,7 +2,9 @@ use std::str::FromStr;
 
 use ruff_macros::{ViolationMetadata, derive_message_formats};
 use ruff_python_ast::{self as ast, Expr};
-use ruff_python_literal::cformat::{CFormatPart, CFormatString, CFormatType};
+use ruff_python_literal::cformat::{
+    CConversionFlags, CFormatPart, CFormatSpec, CFormatString, CFormatType,
+};
 use ruff_python_literal::format::FormatConversion;
 use ruff_text_size::Ranged;
 
@@ -195,7 +197,8 @@ pub(crate) fn logging_eager_conversion(checker: &Checker, call: &ast::ExprCall)
                 }
                 // %s with oct() - suggest using %#o instead
                 FormatConversion::Str
-                    if checker.semantic().match_builtin_expr(func.as_ref(), "oct") =>
+                    if checker.semantic().match_builtin_expr(func.as_ref(), "oct")
+                        && !has_complex_conversion_specifier(spec) =>
                 {
                     checker.report_diagnostic(
                         LoggingEagerConversion {
@@ -207,7 +210,8 @@ pub(crate) fn logging_eager_conversion(checker: &Checker, call: &ast::ExprCall)
                 }
                 // %s with hex() - suggest using %#x instead
                 FormatConversion::Str
-                    if checker.semantic().match_builtin_expr(func.as_ref(), "hex") =>
+                    if checker.semantic().match_builtin_expr(func.as_ref(), "hex")
+                        && !has_complex_conversion_specifier(spec) =>
                 {
                     checker.report_diagnostic(
                         LoggingEagerConversion {
@@ -222,3 +226,23 @@ pub(crate) fn logging_eager_conversion(checker: &Checker, call: &ast::ExprCall)
         }
     }
 }
+
+/// Check if a conversion specifier has complex flags or precision that make `oct()` or `hex()` necessary.
+///
+/// Returns `true` if any of these conditions are met:
+/// - Flag `0` (zero-pad) is used, flag `-` (left-adjust) is not used, and minimum width is specified
+/// - Flag ` ` (blank sign) is used
+/// - Flag `+` (sign char) is used
+/// - Precision is specified
+fn has_complex_conversion_specifier(spec: &CFormatSpec) -> bool {
+    if spec.flags.intersects(CConversionFlags::ZERO_PAD)
+        && !spec.flags.intersects(CConversionFlags::LEFT_ADJUST)
+        && spec.min_field_width.is_some()
+    {
+        return true;
+    }
+
+    spec.flags
+        .intersects(CConversionFlags::BLANK_SIGN | CConversionFlags::SIGN_CHAR)
+        || spec.precision.is_some()
+}