Background Pressure ulcers (also known as pressure sores, decubitus ulcers or bedsores) are localised injuries to the skin or underlying tissue, or both. Pressure ulcers are a disabling consequence of immobility. Electrical stimulation (ES) is widely used for the treatment of pressure ulcers. However, it is not clear whether ES is effective. Objectives To determine the effects (benefits and harms) of electrical stimulation (ES) for treating pressure ulcers. Search methods In July 2019 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In‐Process & Other Non‐Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta‐analyses and health technology reports to identify additional studies. We did not impose any restrictions with respect to language, date of publication or study setting. Selection criteria We included published and unpublished randomised controlled trials (RCTs) comparing ES (plus standard care) with sham/no ES (plus standard care) for treating pressure ulcers. Data collection and analysis Two review authors independently selected trials for inclusion, extracted data, and assessed risk of bias. We assessed the certainty of evidence using GRADE. Main results We included 20 studies with 913 participants. The mean age of participants ranged from 26 to 83 years; 50% were male. ES was administered for a median (interquartile range (IQR)) duration of five (4 to 8) hours per week. The chronicity of the pressure ulcers was variable, ranging from a mean of four days to more than 12 months. Most of the pressure ulcers were on the sacral and coccygeal region (30%), and most were stage III (45%). Half the studies were at risk of performance and detection bias, and 25% were at risk of attrition and selective reporting bias. Overall, the GRADE assessment of the certainty of evidence for outcomes was moderate to very low. Nineteen studies were conducted in four different settings, including rehabilitation and geriatric hospitals, medical centres, a residential care centre, and a community‐based centre. ES probably increases the proportion of pressure ulcers healed compared with no ES (risk ratio (RR) 1.99, 95% confidence interval (CI) 1.39 to 2.85; I2 = 0%; 11 studies, 501 participants (512 pressure ulcers)). We downgraded the evidence to moderate certainty due to risk of bias. It is uncertain whether ES decreases pressure ulcer severity on a composite measure compared with no ES (mean difference (MD) ‐2.43, 95% CI ‐6.14 to 1.28; 1 study, 15 participants (15 pressure ulcers) and whether ES decreases the surface area of pressure ulcers when compared with no ES (12 studies; 494 participants (505 pressure ulcers)). Data for the surface area of pressure ulcers were not pooled because there was considerable statistical heterogeneity between studies (I2 = 96%) but the point estimates for the MD of each study ranged from ‐0.90 cm2 to 10.37 cm2. We downgraded the evidence to very low certainty due to risk of bias, inconsistency and imprecision. It is uncertain whether ES decreases the time to complete healing of pressure ulcers compared with no ES (hazard ratio (HR) 1.06, 95% CI 0.47 to 2.41; I2 = 0%; 2 studies, 55 participants (55 pressure ulcers)). We downgraded the evidence to very low certainty due to risk of bias, indirectness and imprecision. ES may be associated with an excess of, or difference in, adverse events (13 studies; 586 participants (602 pressure ulcers)). Data for adverse events were not pooled but the types of reported adverse events included skin redness, itchy skin, dizziness and delusions, deterioration of the pressure ulcer, limb amputation, and occasionally death. We downgraded the evidence to low certainty due to risk of selection and attrition bias and imprecision. ES probably increases the rate of pressure ulcer healing compared with no ES (MD 4.59% per week, 95% CI 3.49 to 5.69; I2 = 25%; 12 studies, 561 participants (613 pressure ulcers)). We downgraded the evidence to moderate certainty due to risk of bias. We did not find any studies that looked at quality of life, depression, or consumers' perception of treatment effectiveness. Authors' conclusions ES probably increases the proportion of pressure ulcers healed and the rate of pressure ulcer healing (moderate certainty evidence), but its effect on time to complete healing is uncertain compared with no ES (very low certainty evidence). It is also uncertain whether ES decreases the surface area of pressure ulcers. The evidence to date is insufficient to support the widespread use of ES for pressure ulcers outside of research. Future research needs to focus on large‐scale trials to determine the effect of ES on all key outcomes.