We investigated the effects of anodal and cathodal electrical stimulation on wound healing. In a randomized controlled trial, we divided 42 male albino guinea pigs into two control (C1 and C2) and four experimental (E1-E4) groups. A 3 cm linear incision was made at the dorsal skin of all guinea pigs. A unidirectional pulse current of 300 to 600 microamperes, 80 pps, and 0.3 ms pulse duration was administered for 1 hour a day. In groups E1 and E3 (anodal), a positive polarity was applied for the first 3 days followed by negative polarity the remaining days. In groups E2 and E4 (cathodal), negative polarity was applied for the first 3 days and positive polarity the remaining days. Groups E1, E2, and C1 were killed on day 14 and E3, E4, and C2 on day 21. We measured the percentage of decrease in wound surface area (daily tracing) and tensile strength (on days 14 and 21). The results indicated that both cathodal and anodal stimulations increased the rate of wound closure. Beginning with day 12, we saw a significant difference in the percentage of the decrease in wound surface between all treatment and control groups (p < 0.05). Ultimate tensile strength and stress increased in the anodal compared with the cathodal and control groups; at the end of day 14, ultimate tensile stress in E1 was significantly greater compared with C1 (p < 0.05). We conclude that electrical stimulation, regardless of polarity regimen, benefits wound healing, but anodal stimulation the first 3 days and cathodal stimulation the remaining days can lead to stronger repaired tissue.