A study on the effect of age at first calving on selected features of lifetime performance was carried out in one of the largest herds of Montbéliarde cows in Poland. Data from 205 culled cows included 12.430 test-day milking results and data pertaining to lifetime performance – length of life and productive life; number of calvings; lifetime actual yield of milk, fat, protein and dry matter; the content of these constituents in the milk; and FPCM per day of life and productive life. The values of the lifetime performance traits of the Montbéliarde cows varied depending on their age at first calving. The most favourable age at first calving for the lifetime performance traits of the Montbéliarde cows was 27–30 months (824–915 days), while calving too early (less than 824 days) or too late (above 1,038 days) was least favourable. Cows calving for the first time at the age of 824–915 days had the most favourable average daily milk yield (26.6 kg), lactation persistence (34.5% decrease), length of life and productive life (3.215 and 2.360 days), number of calvings (5.2), lifetime yield of milk and FPCM (49.330 and 50.104 kg), and lifetime yield of FPCM per day of life and productive life (15.7 and 21.4 kg) in relation to the other groups of cows. Differences in the values of these traits between cows that first calved at the age of 824–915 days and cows calving earliest and latest were statistically significant (P ≤ 0.01).