Objectives: This systematic review was designed to summarize randomized controlled trials of intra-articular administration of non-steroidal anti-inflammatory drugs (NSAIDs) for temporomandibular disorders. Methods: Randomized controlled trials regarding intra-articular injections of non-steroidal anti-inflammatory drugs for temporomandibular disorders were included in the review. The final search was conducted on 16 June 2024 in the Bielefeld Academic Search Engine, PubMed, and Scopus databases. Results: Of the 173 identified studies, 6 were eligible for review. In trials comparing arthrocentesis alone to arthrocentesis with NSAIDs, slight differences in joint pain were noted. For tenoxicam, differences were under 1 point on a 0–10 scale after 4 weeks, with inconsistent results. Piroxicam showed no significant difference, and pain levels were minimal in both groups. For maximum mouth opening (MMO), tenoxicam showed no significant difference. Piroxicam increased MMO by nearly 5 mm, based on one small trial with bias concerns. Conclusions: Currently, there is no strong scientific evidence supporting the injection of NSAIDs into the temporomandibular joint to relieve pain or increase jaw movement. Preliminary reports on piroxicam with arthrocentesis and tenoxicam or diclofenac without rinsing justify further research.