Background: Previous clinical trials have demonstrated that both acupuncture and sham acupuncture exert significant, non-specific effects on treatment outcomes when compared to no-treatment controls. A recently developed framework (mechanisms in orthodox and complementary and alternative medicine-MOCAM) suggests that the non-specific effects of acupuncture originate from multiple domains (e.g. patient characteristics, acupuncturist skill/technique, the patient-acupuncturist relationship, and the acupuncture environment). However, it remains to be determined precisely how these domains influence the non-specific effects of treatment among patients receiving acupuncture and sham acupuncture in clinical trials. Therefore, we conducted a systematic review to synthesize existing qualitative evidence on how trial participants randomized to acupuncture and sham acupuncture groups experience non-specific effects, regardless of the types of medical condition investigated., Methods: This systematic review included primary qualitative studies embedded in randomized controlled trials designed to investigate acupuncture or sham acupuncture interventions. Eligible studies published in English were derived from a search of five international databases. The methodological quality of included studies was evaluated using the Critical Appraisal Skills Programme (CASP) tool. Using a framework synthesis approach, the identified MOCAM framework was adapted based on the synthesis of the available qualitative evidence., Results: A total of 20 studies of high methodological quality were included. Our proposed model indicated that the effects of acupuncture may be increased by maintaining a professional status, applying a holistic treatment approach, practicing empathy, and providing patients with an appropriate explanation of the theory behind acupuncture and sham acupuncture. From the patient's perspective, the efficacy of treatment can be increased by following the lifestyle modification advice provided by acupuncturists, maintaining a positive attitude toward treatment efficacy, actively engaging with acupuncturists during consultation, and making behavioral changes based on experience gained during the trial., Conclusion: The results of this study may provide a basis for improving and standardizing key components of non-specific effects in acupuncture treatment, and for improving the isolation of specific effects in future clinical trials involving acupuncture and sham acupuncture.