Photobiomodulation with low-level laser therapy (PBM-LLLT) has been introduced as a new tool to relieve nipple pain and repair nipple damage in breastfeeding women; however, evidence is needed to assess its effectiveness. The aim was to evaluate the effect of a single application of PBM-LLLT for breastfeeding women with nipple pain and damage; side effects were also collected. We conducted a randomized double-blinded controlled trial with women with nipple damage who were exclusively breastfeeding and rooming-in at Amparo Maternal maternity service, São Paulo, Brazil (May 2016 to May 2017). Women were randomly assigned into laser (n = 40) or control group (n = 40). Intervention was a single irradiation (660 nm, 100 mW, 2 J, 66.66 J/cm2, 3.3 W/cm2, 20 s of irradiation, punctual, and continuous mode) applied directly. Women reported pain levels at recruitment (before and immediately after irradiation), 6 and 24 h after the treatment. Pain level during a breastfeed was assessed using the Visual Analogue Scale (0 to 10). The primary outcome was the level of nipple pain immediately after the laser irradiation. Data were analyzed using hierarchical model and Wald test. At baseline, pain levels were similar (mean of 7.4 in laser group and 7.1 in control group). Women's perception of pain reduced approximately one point in both groups. Thirty-one percent of participants in the laser group (11/36) reported secondary effects, such as tingling (10/36) and pricking (2/36). The laser protocol of a single application was not effective in reducing pain in women with damaged nipples. Tingling sensation may be experienced by women receiving laser treatment for nipple damage.