Cellular senescence refers to a state of irreversible cell cycle arrest that can be induced by various cellular stresses and is known to play a pivotal role in tumour suppression. While senescence‐associated growth arrest can inhibit the proliferation of cancer‐prone cells, the altered secretory profile of senescent cells, termed the senescence‐associated secretory phenotype, can contribute to the microenvironment that promotes tumour development. Although the senescence‐associated secretory phenotype and its effects on tumorigenesis are both highly context dependent, mechanisms underlying such diversity are becoming better understood, thereby allowing the creation of new strategies to effectively target the senescence‐associated secretory phenotype and senescent cells for cancer therapy. In this review, we discuss the current knowledge on cellular senescence and the senescence‐associated secretory phenotype to develop a structural understanding of their roles in the tumour microenvironment and provide perspectives for future research, including the possibility of senotherapy for the treatment of cancer.