We report an unplanned pregnancy in an HIV-positive woman in her 20s who was undergoing treatment for 6 months with alectinib (Alecensa) for stage IV non-small-cell lung carcinoma. Anaplastic lymphoma kinase (ALK)-tyrosine kinase inhibitor alectinib, a molecule that inhibits proteins involved in tumour cell growth, is the recommended first-line treatment option in case of ALK mutation. Although the patient was informed of the need for definitive contraception, she became pregnant during the treatment with alectinib. A complete tumour response was observed at the time the pregnancy was discovered. Treatment discontinuation was proposed as the patient wanted to keep the pregnancy. Alectinib was temporarily stopped throughout the remaining pregnancy period inline with the patient’s wishes. The pregnancy was uncomplicated. She delivered a healthy female baby vaginally, with treatment being resumed after delivery. After 34 follow-up months, the patient remained in oncological remission and the child’s physical development is normal.