Cancer-related pain is complex and multi-dimensional; yet, the mainstay of cancer pain management has been the biomedical approach. There is a need for nonpharmacological and innovative pain management strategies. Transcutaneous electrical nerve stimulation (TENS) may have a role. The aim of this systematic review was to determine the effectiveness of TENS for cancer-related pain in adults. The Cochrane Library, MEDLINE, EMBASE, CINAHL, PsychINFO, AMED, and PEDro databases were searched for randomized controlled trials (RCTs) investigating the use of TENS for the management of cancer-related pain in adults. Once relevant studies were identified, two pairs of reviewers assessed eligibility for inclusion in the review based on a study eligibility form and using the 5-point Oxford Quality Scale. Two RCTs met the study eligibility criteria (these involved 64 patients). These studies were heterogeneous with respect to study population, methodology, and outcome measures. This prevented meta-analysis. In one RCT, there were no significant differences between TENS and placebo in women with chronic pain secondary to breast cancer treatment. In the other RCT, there were no significant differences between acupuncture-like TENS (AL-TENS) and sham in palliative care patients; this study was significantly underpowered. There is insufficient available evidence to determine the effectiveness of TENS in treating cancer-related pain. Further research is needed to help guide clinical practice, and large multi-center RCTs are required to assess the value of TENS in the management of cancer-related pain in adults.