Background Empirical research on best practices in suicide prevention text intervention is scarce. We present analyses of exchanges concerning suicide on the Canadian Suicide Prevention Service (CSPS) text helpline. Objective To describe the users of the CSPS text service, explore the perceived impact of the service, and identify intervention characteristics associated with a greater likelihood of positive or negative effects of the exchanges. Methods We analyzed data from 112 transcripts using quantitative content analysis, counselor assessments of the calls, and responses by callers to pre-call questionnaires. Results Counselors infrequently conducted a complete suicide risk assessment, but almost always thoroughly explored resources and discussed possible solutions to callers' problems. An operational action plan was rarely developed. Only one technique, reinforcing a strength or a positive action of the caller, was a significant predictor of positive effects of the call. The number of words exchanged during the intervention was positively correlated with the completeness of explorations of resources and solutions and the development of an action plan. Conclusions High-quality effective interventions can be delivered via text messages. Using reinforcement of strengths and encouraging longer calls is recommended. Intervention effects were comparable to those reported in studies of telephone and chat services.