diff --git a/NEWS.md b/NEWS.md
index c7f8a724..5bf07c57 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,6 +4,10 @@
 
 * Added support for `base::cummax()` (#323).
 
+## Bug fixes
+
+* Fix `NA` handling in `cummin()`, `cumprod()`, `cumsum()` (#Yousa-Mirage, #326).
+
 # tidypolars 0.17.0
 
 `tidypolars` requires `polars` >= 1.9.0 and `dplyr` >= 1.2.0.
diff --git a/R/funs-default.R b/R/funs-default.R
index 2aacab8e..b5f25c71 100644
--- a/R/funs-default.R
+++ b/R/funs-default.R
@@ -103,22 +103,28 @@ pl_cosh <- function(x, ...) {
 
 pl_cummax <- function(x, ...) {
   check_empty_dots(...)
-  x$cum_max()
+  # Once a missing value is seen, keep a TRUE mask for all following rows.
+  has_seen_na <- x$is_null()$cum_max()
+  # Replace cumulative results with NA from the first missing value onward.
+  pl$when(has_seen_na)$then(pl$lit(NA))$otherwise(x$cum_max())
 }
 
 pl_cummin <- function(x, ...) {
   check_empty_dots(...)
-  x$cum_min()
+  has_seen_na <- x$is_null()$cum_max()
+  pl$when(has_seen_na)$then(pl$lit(NA))$otherwise(x$cum_min())
 }
 
 pl_cumprod <- function(x, ...) {
   check_empty_dots(...)
-  x$cum_prod()
+  has_seen_na <- x$is_null()$cum_max()
+  pl$when(has_seen_na)$then(pl$lit(NA))$otherwise(x$cum_prod())
 }
 
 pl_cumsum <- function(x, ...) {
   check_empty_dots(...)
-  x$cum_sum()
+  has_seen_na <- x$is_null()$cum_max()
+  pl$when(has_seen_na)$then(pl$lit(NA))$otherwise(x$cum_sum())
 }
 
 # TODO: this is not tested anymore because it requires reframe():
diff --git a/tests/testthat/test-funs_math-lazy.R b/tests/testthat/test-funs_math-lazy.R
index de3e6ca1..0ac99954 100644
--- a/tests/testthat/test-funs_math-lazy.R
+++ b/tests/testthat/test-funs_math-lazy.R
@@ -9,7 +9,6 @@ test_that("mathematical functions work", {
     value = sample(11:15),
     value_trigo = seq(0, 0.4, 0.1),
     value_mix = -2:2,
-    value_with_NA = c(-2, -1, NA, 1, 2)
   )
   test_pl <- as_polars_lf(test)
 
@@ -76,6 +75,77 @@ test_that("mathematical functions work", {
   }
 })
 
+test_that("mathematical functions work with NA", {
+  test <- tibble(
+    value_with_NA = c(11, 12, NA, 14, 15),
+    value_trigo_with_NA = c(0, 0.1, NA, 0.3, 0.4),
+    value_mix_with_NA = c(-2, -1, NA, 1, 2)
+  )
+  test_pl <- as_polars_lf(test)
+
+  for (i in c(
+    "abs",
+    "acos",
+    "acosh",
+    "asin",
+    "asinh",
+    "atan",
+    "atanh",
+    "ceiling",
+    "cos",
+    "cosh",
+    "cummax",
+    "cummin",
+    "cumprod",
+    "cumsum",
+    "exp",
+    "first",
+    "floor",
+    "last",
+    "log",
+    "log10",
+    # "rank", inconsistent behavior between R and Polars with NA
+    "sign",
+    "sin",
+    "sinh",
+    # "sort", inconsistent behavior between R and Polars with NA
+    "sqrt",
+    "tan",
+    "tanh"
+  )) {
+    if (
+      i %in%
+        c(
+          "acos",
+          "asin",
+          "atan",
+          "atanh",
+          "ceiling",
+          "cos",
+          "floor",
+          "sin",
+          "tan"
+        )
+    ) {
+      variable <- "value_trigo_with_NA"
+    } else if (i %in% c("abs", "mean")) {
+      variable <- "value_mix_with_NA"
+    } else {
+      variable <- "value_with_NA"
+    }
+
+    pol <- paste0("mutate(test_pl, foo =", i, "(", variable, "))") |>
+      str2lang() |>
+      eval()
+
+    res <- paste0("mutate(test, foo =", i, "(", variable, "))") |>
+      str2lang() |>
+      eval()
+
+    expect_equal_lazy(pol, res, info = i)
+  }
+})
+
 test_that("warns if unknown args", {
   test <- tibble(
     x1 = c("a", "a", "b", "a", "c"),
diff --git a/tests/testthat/test-funs_math.R b/tests/testthat/test-funs_math.R
index c1310955..ae6a21f4 100644
--- a/tests/testthat/test-funs_math.R
+++ b/tests/testthat/test-funs_math.R
@@ -5,7 +5,6 @@ test_that("mathematical functions work", {
     value = sample(11:15),
     value_trigo = seq(0, 0.4, 0.1),
     value_mix = -2:2,
-    value_with_NA = c(-2, -1, NA, 1, 2)
   )
   test_pl <- as_polars_df(test)
 
@@ -72,6 +71,77 @@ test_that("mathematical functions work", {
   }
 })
 
+test_that("mathematical functions work with NA", {
+  test <- tibble(
+    value_with_NA = c(11, 12, NA, 14, 15),
+    value_trigo_with_NA = c(0, 0.1, NA, 0.3, 0.4),
+    value_mix_with_NA = c(-2, -1, NA, 1, 2)
+  )
+  test_pl <- as_polars_df(test)
+
+  for (i in c(
+    "abs",
+    "acos",
+    "acosh",
+    "asin",
+    "asinh",
+    "atan",
+    "atanh",
+    "ceiling",
+    "cos",
+    "cosh",
+    "cummax",
+    "cummin",
+    "cumprod",
+    "cumsum",
+    "exp",
+    "first",
+    "floor",
+    "last",
+    "log",
+    "log10",
+    # "rank", inconsistent behavior between R and Polars with NA
+    "sign",
+    "sin",
+    "sinh",
+    # "sort", inconsistent behavior between R and Polars with NA
+    "sqrt",
+    "tan",
+    "tanh"
+  )) {
+    if (
+      i %in%
+        c(
+          "acos",
+          "asin",
+          "atan",
+          "atanh",
+          "ceiling",
+          "cos",
+          "floor",
+          "sin",
+          "tan"
+        )
+    ) {
+      variable <- "value_trigo_with_NA"
+    } else if (i %in% c("abs", "mean")) {
+      variable <- "value_mix_with_NA"
+    } else {
+      variable <- "value_with_NA"
+    }
+
+    pol <- paste0("mutate(test_pl, foo =", i, "(", variable, "))") |>
+      str2lang() |>
+      eval()
+
+    res <- paste0("mutate(test, foo =", i, "(", variable, "))") |>
+      str2lang() |>
+      eval()
+
+    expect_equal(pol, res, info = i)
+  }
+})
+
 test_that("warns if unknown args", {
   test <- tibble(
     x1 = c("a", "a", "b", "a", "c"),