The purpose of this study was to evaluate the efficacy of custom thermoplastic splinting designed to limit metacarpalphalangeal (MCP) joint flexion for trigger finger as a first treatment option. This study was a single group, prepost design with 28 participants fit with a low-profile custom thermoplastic MCP blocking (ring) splint. The pre- and post outcome measures included: stages of stenosing tenosynovitis (SST), grip strength, Numeric Pain Rating Scale (NPRS), the number of triggering events in ten active fists, and participant perceived improvement in symptoms. These measures were taken at the time of initial assessment before splint fabrication and after six weeks of continuous splint wear. Participants were given an educational handout on trigger finger and exercises to complete independently. After the use of a splint, there were statistically significant improvements in the SST, NPRS, the number of triggering events in ten active fists, and in the participant perceived improvement in symptoms. Grip strength did not significantly change. This study demonstrated a benefit from the use of a custom thermoplastic splint for an isolated incidence of trigger finger based on chosen outcome measures.