Inflammatory bowel disease significantly impairs the patient's quality of life. In young individuals, both the disease and the drugs used for the treatment may impact fertility. Our study aimed to assess the action of new 1,3,4-oxadiazole derivatives of pyrrolo[3,4-d]pyridazinone on the rat testes in a model of TNBS-induced colitis in rats. In the current study, testes from eight randomly chosen rats were taken from each of the following groups: the control group (K), the colitis group (C), and the groups receiving compounds 7b, 10b, and 13b in higher doses (20 mg/kg). Colitis did not affect the testicular index (expressed as a percentage of the body weight), but in group 13b, this parameter was significantly higher than in group K. No significant differences between groups were noticed in malondialdehyde, superoxide dismutase, interleukin-1, or metalloproteinase 9 levels. In the colitis group, lactate dehydrogenase activity in the testes was not increased; however, the administration of compound 10b significantly increased this parameter when compared to both groups K and C. Histological evaluation also did not reveal abnormalities, and the morphology of the testicular tissues was comparable in all groups. The results may suggest that the new 1,3,4-oxadiazole derivatives of pyrrolo[3,4-]pyridazinone did not exert significant testicular toxicity.