diff --git a/libc/src/stdio/printf_core/CMakeLists.txt b/libc/src/stdio/printf_core/CMakeLists.txt
--- a/libc/src/stdio/printf_core/CMakeLists.txt
+++ b/libc/src/stdio/printf_core/CMakeLists.txt
@@ -72,6 +72,7 @@
     .writer
     .core_structs
     libc.src.__support.CPP.limits
+    libc.src.__support.FPUtil.fputil
 )
 
 
diff --git a/libc/src/stdio/printf_core/float_hex_converter.h b/libc/src/stdio/printf_core/float_hex_converter.h
--- a/libc/src/stdio/printf_core/float_hex_converter.h
+++ b/libc/src/stdio/printf_core/float_hex_converter.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FLOAT_HEX_CONVERTER_H
 #define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FLOAT_HEX_CONVERTER_H
 
+#include "src/__support/FPUtil/FEnvImpl.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/stdio/printf_core/converter_utils.h"
 #include "src/stdio/printf_core/core_structs.h"
@@ -133,11 +134,27 @@
 
     mantissa >>= shift_amount;
 
-    // Round to nearest, if it's exactly halfway then round to even.
-    if (truncated_bits > halfway_const)
-      ++mantissa;
-    else if (truncated_bits == halfway_const)
-      mantissa = mantissa + (mantissa & 1);
+    switch (fputil::get_round()) {
+    case FE_TONEAREST:
+      // Round to nearest, if it's exactly halfway then round to even.
+      if (truncated_bits > halfway_const)
+        ++mantissa;
+      else if (truncated_bits == halfway_const)
+        mantissa = mantissa + (mantissa & 1);
+      break;
+    case FE_DOWNWARD:
+      if (truncated_bits > 0 && is_negative) {
+        ++mantissa;
+      }
+      break;
+    case FE_UPWARD:
+      if (truncated_bits > 0 && !is_negative) {
+        ++mantissa;
+      }
+      break;
+    case FE_TOWARDZERO:
+      break;
+    }
 
     // If the rounding caused an overflow, shift the mantissa and adjust the
     // exponent to match.
diff --git a/libc/test/src/stdio/CMakeLists.txt b/libc/test/src/stdio/CMakeLists.txt
--- a/libc/test/src/stdio/CMakeLists.txt
+++ b/libc/test/src/stdio/CMakeLists.txt
@@ -106,6 +106,8 @@
     printf_test.cpp
   DEPENDS
     libc.src.stdio.printf
+    libc.src.fenv.fesetround
+    libc.src.__support.FPUtil.fputil
 )
 
 add_subdirectory(printf_core)
diff --git a/libc/test/src/stdio/sprintf_test.cpp b/libc/test/src/stdio/sprintf_test.cpp
--- a/libc/test/src/stdio/sprintf_test.cpp
+++ b/libc/test/src/stdio/sprintf_test.cpp
@@ -8,6 +8,7 @@
 
 #include "src/stdio/sprintf.h"
 
+#include "src/__support/FPUtil/FEnvImpl.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PlatformDefs.h"
 #include "utils/UnitTest/Test.h"
@@ -601,6 +602,112 @@
   written = __llvm_libc::sprintf(buff, "%5a", -nan);
   ASSERT_STREQ_LEN(written, buff, " -nan");
 
+  // Rounding Mode Tests.
+
+  __llvm_libc::fputil::set_round(FE_TONEAREST);
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.2p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.2p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  __llvm_libc::fputil::set_round(FE_DOWNWARD);
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.2p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.2p+0");
+
+  __llvm_libc::fputil::set_round(FE_UPWARD);
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.2p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.2p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  __llvm_libc::fputil::set_round(FE_TOWARDZERO);
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", 0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.08p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.18p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.04p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.0p+0");
+
+  written = __llvm_libc::sprintf(buff, "%.1a", -0x1.14p0);
+  ASSERT_STREQ_LEN(written, buff, "-0x1.1p+0");
+
+  // The remaining tests assume TONEAREST since it's the default on most
+  // systems.
+  __llvm_libc::fputil::set_round(FE_TONEAREST);
+
   // Precision Tests.
 
   written = __llvm_libc::sprintf(buff, "%.1a", 1.0);