The dung excreted by yaks (Bos grunniens) into alpine grasslands on the Qinghai-Tibetan Plateau is an important ecological pathway for returning organic matter and nutrients that are closely linked to soil fertility and grassland productivity. However, few previous studies have investigated the dynamics of carbon (C) and nitrogen (N) associated with yak dung pats, particularly with respect to C and N leaching. This study experimentally investigated the effects of yak dung pat fragmentation on its C and N dynamics in Northern Tibet. Four treatments were examined: a full-size dung pat (control, FDP) and respectively splitting the full-size dung pat into four (1/4FDP), eight (1/8FDP), and sixteen (1/16FDP) equal-sized pats, each within an identical leaching device and had three replicates. The results showed that fragmentation did not influence (P > 0.05) dung total organic C (TOC) and N (TN) concentrations, but it did cause a decrease (P < 0.05) in both ammonium-N (NH₄⁺-N) and nitrate-N (NO₃⁻-N) concentrations and also reduced the loss of dry matter (P < 0.05), after 72 days of dung decomposition. Cumulative amounts of dissolved organic C (DOC) and N (DON) leached from the dung were significantly higher in the three fragmentation treatments than in the control (respectively 2.46–3.50 vs. 1.64 g C chamber⁻¹, 0.14–0.16 vs. 0.10 g N chamber⁻¹; P < 0.05). However, fragmentation did not always decrease cumulative dung NH₄⁺-N and NO₃⁻-N leaching, and neither NH₄⁺-N nor NO₃⁻-N leaching (P > 0.05) were affected by the 1/4FDP treatment. The DOC leaching accounted for 1.58–3.36 % of the initial dung TOC input, while the DON, NH₄⁺-N, and NO₃⁻-N leaching respectively accounted for 2.34–3.82 %, 0.68–0.87 %, and 0.19–0.27 % of the initial dung TN input. In conclusion, our findings suggest that yak dung pat fragmentation can increase the leaching of DOC and DON and the heavily fragmenting can decrease the leaching of both NH₄⁺-N and NO₃⁻-N after short-term dung decomposition in Northern Tibet.