Turkey is one of the major garlic producing country in the world and the significant amount of Turkey’s production has been made using a garlic variety called Taşköprü garlic (Allium sativum L.) in Kastamonu, Turkey. In order to improve the quality of garlic production, a field experiment was conducted to evaluate the effects of different doses of leonardite organic fertilizer, mineral fertilizer NPK and the mixture of both the leonardite and NPK fertilizers on the soil properties and mean performances of different characters and yield production of Taşköprü garlic. The treatments were: the plots without leonardite and NPK fertilizers (Control), (2) 80 N kg ha-1 + 40 kg ha-1 P2O5 + 100 kg ha-1 K2O (MF), (3) 2.6 ton ha-1 leonardite (Leo1), (4) 6.9 ton ha-1 leonardite (Leo2), (5) 9.7 ton ha-1 leonardite (Leo3), (6) Leo1 + MF, (7) Leo2 + MF and Leo3 + MF. Most soil characteristics and the different characters and yield production of Taşköprü garlic statistically varied between the different fertilizer treatments. The plots with the Leo3MF application showed the highest soil organic C, N, P and K concentrations, and the SOCstock and TNstock, while it had the highest bulb weight, length, equatorial diameter, weight of cloves, width of cloves, length of cloves as well as bulb yield per decare. Of the soil properties, the garlic yield was strongly positively correlated with the soil N concentration, indicating that the applications of leonardite with the different doses or the mixture of leonardite with the mineral fertilizer were resulting in higher soil N concentration and thus having the greatest effect on the garlic yields.