A study investigating the mineral content of field-grown tomatoes was conducted in 2009-2010 in the Garden of the Agricultural Research and Experiment Station of the University of Warmia and Mazury in Olsztyn. Tomatoes (Lycopersicon esculentum Mill.) are grown and consumed throughout the world. The increasing economic significance of tomato fruits is a consequence of their high biological value, specific taste and flavour as well as a wide range of uses and applications. Plastic mulch is used in the large-scale production of thermophilous vegetable crops. The benefits of mulching include an improvement in soil structure and plant nutrient utilisation. The experimental materials comprised three tomato cultivars, ‘Ikarus’, ‘Rumba’ and ‘Złoty Ożarowski’. Tomato plants were grown in bare soil and in soil mulched with black non-woven PP 50 fabric. Seedlings were grown in a greenhouse, in line with the generally observed standards for tomato cultivation. Analyses were performed to determine the effect of cultivar and mulching on the concentrations of selected minerals in tomato fruit. Among the studied tomato cultivars, the fruit of cv. ‘Rumba’ contained the largest amounts of total N and Fe. Mulching had no significant effect on the mineral content of tomato fruit. The fruit harvested from tomato plants grown in bare soil without mulch and in mulched plots were characterised by a normal Ca : Mg ratio and a desirable Ca : P ratio.