In this study, I investigated parenting concerns and worries in parents during cancer treatment and examined the psychometric properties of the Polish version of the Parenting Concerns Questionnaire. Reliability, as well as factorial and convergent validity, were analyzed. A total sample size of 145 parents during cancer treatment (parents of children aged 18 years or younger at the time of the survey) participated in the study. The study was an online survey method conducted between January 2019 and December 2021. Parents were sent a survey link and were requested to fill the Perceived Stress Scale (PSS-10), the Parenting Stress Index (PSI-3-SF), the SF-36v2 Health Survey (SF-36v2), and the Family Resilience Assessment Scale (FRAS). The author received permission for using these questionnaires in online research. Confirmatory factor analysis of the Polish version of the Parenting Concerns Questionnaire did not confirm the original three-factor structure. However, the standardized factor loadings for the three factors were moderate to high. Additionally, apart from high-reliability estimates, this instrument proved to have good convergent and discriminant validity for all three factors. The PCQ-PL demonstrated adequate convergent validity with expected correlations with parenting stress, perceived stress, quality of life, and family resilience. The results suggest that the PCQ-PL is a reliable and relatively valid measurement tool to evaluate the level of parental concerns in Polish patients. The PCQ can be a useful tool to recognize parents with cancer who might need psychological support regarding combining the role of a parent and oncological patient.