A screening assessment of anxiety and depressive symptoms is of great importance for preventing mental health problems in a general population. The study aims (1) to examine the factor structure and invariance measurement of the Polish version of the Patient Health Questionnaire–4 (PHQ–4) developed for measuring anxiety and depressive symptoms, (2) to estimate the prevalence of these symptoms in different age and gender groups from February to July 2022, (3) to identify latent subpopulations within the general population based on the anxiety and depressive symptom levels. The sample included 2557 Polish adults (1730 females, 811 males, and 16 non-binary) aged 18–78 (M = 27.18, SD = 12.29). The Polish version of the PHQ–4 was used. Multi-group confirmatory factor analysis and latent profile analysis (LPA) were applied. The Polish version of the PHQ–4 has a theoretically congruent factor structure and is invariant across age and gender categories. Based on the cut-off scores for the depression and anxiety subscales of ≥ 3, more than half of Poles are screened positively for anxiety and/or depression. We distinguished (by LPA) and described four subpopulations common for both females and males. We identified risk groups for mental disorders (females, non-binary, and younger people in general, as well as unemployed, less educated, and single people). The prevalence of probable anxiety and depressive disorders in the Polish population is extremely high. It is necessary to provide further mental health monitoring and to conduct qualitative research on the psychological reasons for the occurrence of anxiety and depressive symptoms. Mental health monitoring is crucial.