New ⁴⁰K/⁴⁰Ar datings for teschenitic rocks in the Silesian Unit of the Outer Western Carpathians in Poland are presented. Several petrological varieties of intrusions were studied in 5 localities. Dating was performed on monomineral separates of biotites and amphiboles as well as on whole rock samples. The biotite ages (137.9–133.1 Ma — Valanginian) are significantly older than those of amphiboles (112.5–89.9 Ma — Albian–Turonian). Whole rock ages are considerably spread between those two clusters, being concordant either with ”biotite” or ”amphibole” dates or much younger. Interpretation of data poses some problems because evidence exists for hydrothermal alterations, which might influence Ar content in both minerals. Older, biotite ages are interpreted as more reliable crystallization ages, since they are close to the age of surrounding sediments and are concordant with field observations that intrusions in some cases are almost surficial. Amphibole ages are probably affected by Ar loss due to hydrothermal activity. Comparison with recently published ⁴⁰Ar/³⁹Ar datings implies that the duration of the teschenitic and related magmatism in the Silesian Basin was probably from Valanginian up to Barremian–Aptian (ca. 15 Ma).