The antineoplastic effects of thymoquinone (TQ) (which has antioxidant and anticarcinogenic effects) on neoplastic changes (atypical acinar cell foci, AACF) induced by azaserine were investigated, for the first time. Rats were randomly divided into five groups of 10 rats each (Cont, Tim, Az, AzTim1, and AzTim2). The Cont group was fed only with a standard diet. TQ (50 mg/L) was given orally (P.O.) to the Tim, AzTim1, and AzTim2 groups. TQ was given to Tim and AzTim1 after the first month, while AzTim2 group rats were given after the third month of azaserine injection, when AACFs began to form. Azaserine was injected intraperitoneally (i.p.) (30 mg/kg bw) to 2-weeks-old Wistar albino male rats in the Az, AzTim1, and AzTim2 groups. AACF load were observed to be statistically significantly higher in all categories in the Az group compared to the Cont group (p < 0.05). AACF load were statistically significantly lower in all TQ groups (AzTim1 and AzTim2) compared to the Az group and it was demonstrated with TQ-containing diet administration. This decrease indicates the antineoplastic effect of TQ on AACF and supports previous studies.