Introduction. Adolescent sport participation has changed in New Zealand (NZ) over recent years with increasing opportunities for young children to follow specialised, intensive and highly structured sport pathways. There have been anecdotal reports of a corresponding increase in injuries in 10–13-year-old NZ children, particularly gradual onset injuries. Overseas research suggests early specialisation and high participation volumes are associated with musculoskeletal injury, yet a recent systematic review highlighted the need for more research on this topic. Aim. To investigate the degree of early specialisation and sport participation volumes of 10–13-year-old NZ children and examine the associations of these variables with injury history. Methods. Children who attended the 2017 NZ Association of Intermediate and Middle Schools games were eligible to participate in this retrospective cross-sectional study. A survey was used to collect information regarding the degree of specialisation (high, moderate or low), sport participation volume, free-play volume and injuries sustained in the previous 12 months. Multiple logistic regression analyses were used to investigate the associations between each of specialisation and participation volume, and the likelihood of reporting a history of injury. Results. Nine hundred and fourteen children (538 female; mean age [SD] 12.6±0.5) completed the questionnaire. The point prevalence of high specialisation was 25%. The median weekly sport participation volume was 4.4 hours (range 0.25–38 hours). Seventy-four percent of children reported a history of injury in the past 12 months (78% acute, 22% gradual onset). After adjusting for age, gender and participation volume, the odds of reporting an injury history for highly specialised children was not significantly higher than children with low specialisation (OR = 0.88; CI = 0.59–1.31; p = 0.53). Average weekly participation volume was associated with increased odds of reporting 'any injury' (OR = 1.07; CI = 1.02–1.12; p < 0.01) or 'gradual onset injury' (OR = 1.09; CI = 1.05–1.14; p < 0.01), even when adjusting for specialisation, age, school size and decile. Children participating in more hours of sport per week than age in years (OR = 2.42; CI = 1.27–4.62; p = 0.02), playing a single sport for more than 8 months of the year (OR = 1.60; CI = 1.07–2.36; p = 0.02), or exceeding a 2:1 ratio of organised to free-play hours per week (OR = 1.52; CI = 1.08–2.15; p = 0.02), had increased odds of reporting a 'gradual onset injury'. Conclusion. Being highly specialised in one sport did not increase the odds of reporting a history of injury in this group of 10–13-year-old NZ children. This finding is contrary to overseas reports, perhaps due to differences in the age groups studied. Participating in higher weekly volumes of organised sport was associated with increased odds of reporting an injury or a gradual onset injury in the previous 12 months. The findings support previous recommendations to not participate in one sport for more than 8 months of the year, not participate in organised sport for more hours per week than years of age, and not exceed a 2:1 ratio of organised sport to free-play.