Purpose: Nutrition plays an important role in cancer survivorship. This systematic review and meta-analysis aim to critically assess and quantify the effectiveness of nutrition care interventions provided by dietitians to survivors who have completed treatment for cancer. Methods: A systematic review of randomized controlled trials (RCTs) published from January 2004 to November 2023 reporting the effectiveness of primary care dietetic interventions with adult cancer survivors was conducted. PubMed, Scopus, CINAHL, Embase, ProQuest and PsycINFO databases were searched for key terms. Meta-analyses were conducted where there were sufficient studies of the same cancer type and outcomes. Results: Twelve RCTs representing 1138 cancer survivors (519 breast cancer; 75 prostate cancer; 544 colorectal cancer) were included. Primary outcome measures included weight loss (n = 6), quality of life (n = 2), reducing lymphedema-related arm volume (n = 2), nutritional status (n = 1) and increasing fruit and vegetable intake (n = 1). Weight loss was observed in studies where this was the primary outcome. Results for quality of life varied. Meta-analyses of RCTs with breast cancer survivors showed that dietitian intervention achieved a mean of 3.7 kg greater intentional weight loss and 2.3% greater body fat decrease than control (p < 0.0001). Conclusions: This study provides evidence for the effectiveness of primary care dietetic interventions by dietitians with cancer survivors, particularly with respect to intentional weight and fat loss in breast cancer survivors. Implications for cancer survivors: Dietitians can play a key role in managing weight and improving long term health outcomes and prognosis for cancer survivors beyond the acute care setting.