Abstract In recent years, photodynamic therapy (PDT) has been advised as a possible adjunct to conventional therapy for acne vulgaris (acne). Both the 2021 National Institute for Health and Care Excellence acne guidelines and the 2018 British Association of Dermatologists’ PDT guidelines include PDT as an option to consider for acne in those aged 18 and older and if other treatments are ineffective, not tolerated or contraindicated. There is, at present, insufficient evidence to suggest an exact dosage or treatment protocol. Herein, we present a case of successful use of PDT in a patient with difficult-to-manage acne and the protocol employed. A 21-year-old woman has been attending dermatology for 10 years for acne, with keloid scarring, which is most extensive on her back. She was previously treated with spironolactone and a combined oral contraceptive pill. Topical retinoids and antibiotics, including trimethoprim (to which she developed erythema multiforme), clindamycin, azithromycin and tetracyclines, had all been used for various periods without sustained successful clearance. The patient has a general anxiety disorder with low mood and is taking quetiapine. She is a social media advocate for people with mental health issues and has good insight into her mood. She is educated regarding isotretinoin and contraindications to its use. The patient was treated with a trial of two sessions of PDT 1 week apart. The target area was prepared 3 h in advance of light with methyl aminolaevulinate 16% (as hydrochloride) spread to a thickness of 1–5 mm beyond the area border. Red light (635 nm) with a total dose of 37 J cm−2 was provided for 7 min and 50 s each time. The patient has Fitzpatrick skin type I and experienced moderate postprocedural erythema, which later resolved. At both the 3- and 6-month clinical follow-up, the patient is effectively clear of active acne in the treated area. There is previous residual scarring. The patient is not using any topical or systemic acne treatments. Options for acne treatment are diverse. However, some patients experience ineffective clearance or tolerance, and are not good candidates for isotretinoin. Dermatology centres with PDT may help provide an alternative solution. This case illustrates the successful application of PDT for acne and adds to the body of literature to support its inclusion in the aforementioned guidelines.