Tottering (Tg) mice carry the mutation P601L in their Cacna1a encoded Ca_v2.1 channels. Transmitter release at the wild-type neuromuscular junction (NMJ) is almost exclusively mediated by Ca_v2.1 channels, and we use this model synapse to study synaptic consequences of the Tg mutation. With electrophysiology, and using subtype-specific Ca_v2 channel-blocking toxins, we assessed a possible compensatory contribution of non-Ca_v2.1 channels to evoked acetylcholine (ACh) release at Tg NMJs. Release was reduced by ~75% by the Ca_v2.1 channel blocker -agatoxin-IVA, which was less than the ~95% reduction observed in wild-type. Release at Tg NMJs, but not at wild-type synapses, was reduced by ~15% by SNX-482, a Ca_v2.3 channel blocker. No Ca_v2.2 channel involvement was found. Probably, there is a small reduction in functional presynaptic Ca_v2.1 channels at Tg NMJs, which is compensated for by Ca_v2.3 channels. The remaining Ca_v2.1 channels are likely to convey enlarged Ca²⁺ flux, because evoked ACh release at Tg NMJs, at low extracellular Ca²⁺ concentration, was ~6-fold higher than at wild-type NMJs. This is the first report of compensatory expression of non-Ca_v2.1 channels at NMJs of mice with a single amino acid change in Ca_v2.1.