Background The amount of tissue trauma within second‐degree perineal tears varies widely. Therefore, subcategorization of second‐degree tears and a better understanding of their occurrence and risk factors are needed. The aim of this study was to assess the occurrence of perineal tears when second‐degree tears were subcategorized. Furthermore, we aimed to assess the association between variables related to perineal anatomy and other potential risk factors, with second‐degree tear subcategories. Methods This prospective cohort study included 880 primiparous and multiparous women giving birth to one child vaginally. Perineal tears were categorized using the classification system recommended by the Royal College of Obstetricians and Gynaecologists. In addition, second‐degree tears were subcategorized as 2A, 2B, or 2C according to the percentage of damage to the perineal body. Selected variables related to perineal anatomy were as follows: length of genital hiatus; perineal body length; and previous perineal trauma. Risk factors for second‐degree tear subcategories were analyzed using a multinominal regression model. Results Perineal tears occurred as follows: first‐degree: 35.6% (n = 313), 2A: 16.3% (n = 143), 2B: 9.1% (n = 80), 2C: 6.6% (n = 58), and third‐ or fourth‐degree: 1.6% (n = 14). In total, 169/880 participants underwent an episiotomy. When episiotomies were excluded, the risk for 2B, or 2C tears increased with smaller genital hiatus, larger perineal body, previous perineal trauma, primiparity, higher gestational age, instrumental vaginal delivery and fetal presentation other than occiput anterior. Conclusion The occurrence of second‐degree tear subcategories was 16.3% for 2A tears, 9.1% for 2B tears, and 6.6% for 2C tears. Factors related to perineal anatomy increased the odds for experiencing a second‐degree tear in a more severe subcategory. The extent of tissue trauma within the second‐degree perineal tear category varies widely. There is a need for a better understanding of the occurrence and risk factors for larger second‐degree tears, as second‐degree tears of greater severity may impact post‐partum pelvic floor health. In this study, a subclassification system for second‐degree tears was used. The overall occurrence of second‐degree tear subcategories was 16.3% for 2A tears, 9.1% for 2B tears, and 6.6% for 2C tears. Differences in perineal anatomy, primiparity, and factors associated with a more complicated birth significantly increased the odds for experiencing a second‐degree tear in a more severe subcategory.