This study aims to evaluate the agreement in maximum oxygen consumption (V˙O2max) between a running protocol and a ski mountaineering (SKIMO) protocol. Eighteen (eleven males, seven females) ski mountaineers (age: 25 ± 3 years) participated in the study. V˙O2max, maximum heart rate (HRmax), and maximum blood lactate concentration (BLAmax) were determined in an incremental uphill running test and an incremental SKIMO-equipment-specific test. V˙O2max did not differ between the SKIMO and uphill running protocols (p = 0.927; mean difference –0.07 ± 3.3 mL/min/kg), nor did HRmax (p = 0.587, mean difference –0.7 ± 5.1 bpm). A significant correlation was found between V˙O2max SKIMO and V˙O2max running (p ≤ 0.001; ICC = 0.862 (95% CI: 0.670−0.946)). The coefficient of variation was 4.4% (95% CI: 3.3−6.5). BLAmax was significantly lower for SKIMO compared to running (12.0 ± 14.1%; p = 0.002). This study demonstrates that V˙O2max determined with a traditional uphill running protocol demonstrates good agreement with an equipment-specific SKIMO protocol.