diff --git a/.github/workflows/nightly-verify.yml b/.github/workflows/nightly-verify.yml
index 3142c329bf..5e7106fccc 100644
--- a/.github/workflows/nightly-verify.yml
+++ b/.github/workflows/nightly-verify.yml
@@ -185,6 +185,10 @@ jobs:
           # Required for macOS
           export CXXFLAGS="${CXXFLAGS} -D_LIBCPP_DISABLE_AVAILABILITY"
           echo "CXXFLAGS=${CXXFLAGS}"
+          if [[ $(uname) == "Linux" ]]; then
+            # conda-forge's R makevars doesn't seem to define CXX20 on Linux
+            export R_MAKEVARS_USER="$(pwd)/arrow-adbc/ci/r_makevars_cxx20"
+          fi
           ./arrow-adbc/dev/release/verify-release-candidate.sh $VERSION 0
 
       - name: Verify
diff --git a/.github/workflows/verify.yml b/.github/workflows/verify.yml
index a792b88021..e822eaaa3a 100644
--- a/.github/workflows/verify.yml
+++ b/.github/workflows/verify.yml
@@ -132,6 +132,10 @@ jobs:
           # Required for macOS
           export CXXFLAGS="${CXXFLAGS} -D_LIBCPP_DISABLE_AVAILABILITY"
           echo "CXXFLAGS=${CXXFLAGS}"
+          if [[ $(uname) == "Linux" ]]; then
+            # conda-forge's R makevars doesn't seem to define CXX20 on Linux
+            export R_MAKEVARS_USER="$(pwd)/ci/r_makevars_cxx20"
+          fi
           ./dev/release/verify-release-candidate.sh ${INPUTS_VERSION} ${INPUTS_RC}
       - name: Verify
         if: matrix.os == 'windows-latest'