diff --git a/cpp/src/arrow/dataset/scanner.cc b/cpp/src/arrow/dataset/scanner.cc
index 4e679eea661..fcefeda582b 100644
--- a/cpp/src/arrow/dataset/scanner.cc
+++ b/cpp/src/arrow/dataset/scanner.cc
@@ -141,19 +141,17 @@ Result<std::shared_ptr<Schema>> GetProjectedSchemaFromExpression(
     if (call->function_name != "make_struct") {
       return Status::Invalid("Top level projection expression call must be make_struct");
     }
-    for (const compute::Expression& arg : call->arguments) {
-      if (auto field_ref = arg.field_ref()) {
-        if (field_ref->IsName()) {
-          field_names.emplace(*field_ref->name());
-        } else if (field_ref->IsNested()) {
-          // We keep the top-level field name.
-          auto nested_field_refs = *field_ref->nested_refs();
-          field_names.emplace(*nested_field_refs[0].name());
-        } else {
-          return Status::Invalid(
-              "No projected schema was supplied and we could not infer the projected "
-              "schema from the projection expression.");
-        }
+    for (auto field_ref : compute::FieldsInExpression(projection)) {
+      if (field_ref.IsName()) {
+        field_names.emplace(*field_ref.name());
+      } else if (field_ref.IsNested()) {
+        // We keep the top-level field name.
+        auto nested_field_refs = *field_ref.nested_refs();
+        field_names.emplace(*nested_field_refs[0].name());
+      } else {
+        return Status::Invalid(
+            "No projected schema was supplied and we could not infer the projected "
+            "schema from the projection expression.");
       }
     }
   }
diff --git a/r/tests/testthat/test-dplyr-query.R b/r/tests/testthat/test-dplyr-query.R
index 469bcd10aa6..00a9784e801 100644
--- a/r/tests/testthat/test-dplyr-query.R
+++ b/r/tests/testthat/test-dplyr-query.R
@@ -740,12 +740,19 @@ test_that("Can use nested field refs", {
       collect(),
     nested_data
   )
+})
 
-  # Now with Dataset: make sure column pushdown in ScanNode works
+test_that("Can use nested field refs with Dataset", {
   skip_if_not_available("dataset")
+  # Now with Dataset: make sure column pushdown in ScanNode works
+  nested_data <- tibble(int = 1:5, df_col = tibble(a = 6:10, b = 11:15))
+  tf <- tempfile()
+  dir.create(tf)
+  write_dataset(nested_data, tf)
+  ds <- open_dataset(tf)
+
   expect_equal(
-    nested_data %>%
-      InMemoryDataset$create() %>%
+    ds %>%
       mutate(
         nested = df_col$a,
         times2 = df_col$a * 2
@@ -759,6 +766,15 @@ test_that("Can use nested field refs", {
       ) %>%
       filter(nested > 7)
   )
+  # Issue #34519: error when projecting same name, but only on file dataset
+  expect_equal(
+    ds %>%
+      mutate(int = as.numeric(int)) %>%
+      collect(),
+    nested_data %>%
+      mutate(int = as.numeric(int)) %>%
+      collect()
+  )
 })
 
 test_that("Use struct_field for $ on non-field-ref", {