We consider scalar field perturbations in the background of black holes immersed in perfect fluid dark matter (PFDM). We find, by using the sixth-order Wentzel-Kramers-Brillouin (WKB) approximation, that the longest-lived modes are those with a higher angular number for a scalar field mass smaller than a critical value, known as the anomalous decay rate of the quasinormal modes, while beyond this critical value the opposite behavior is observed. Moreover, we show that it is possible to recover the real part of the quasinormal frequencies (QNFs), the imaginary part of the QNFs, and the critical scalar field mass of the Schwarzschild background for different values of the PFDM intensity parameter k. For values of k smaller than these values, the abovementioned quantities are greater than the Schwarzschild background. However, beyond these values of k, these quantities are smaller than the Schwarzschild background.