Among a group of First Nations youth, this research aimed to obtain objective measures of anthropometry, physical activity (PA) and fitness; to identify any group-level differences by sex, body mass index, waist circumference and body fat categories; to assess the barriers and supports to PA. Youth participated in anthropometric measures (BMI, waist circumference, body fat percentage), PA assessment (3 days of accelerometry) and fitness testing (guided by the Canadian Physical Activity, Fitness and Lifestyle Approach). Barriers and supports were assessed via environmental scan and focus groups. Descriptive statistics were compared to reference data. Group differences by sex, BMI status, waist circumference and body fat categories were tested using Mann-Whitney U and Chi square tests (p ≤ 0.05). Qualitative data were assembled into one file and coded manually for categories and themes. Seventy-two youth (12.1 ± 1.1 years, 61.1% male) participated in at least one measure; 36 completed the accelerometry. Sixty-three percent were overweight or obese, 51% were abdominally obese and 21% had excess body fat. Most (86.1%) met Canada's PA guidelines. Boys were more active than girls (p = 0.025) and had greater cardiorespiratory endurance (p = 0.003). Overweight, obese, or abdominally obese youth had lower cardiorespiratory endurance than normal weight youth (p < 0.001). Barriers and supports fell under the main themes: motivation, role models, personnel and facilities, environment and programs. Based on this assessment, youth in this community are active, but not sufficiently physically fit, especially among those affected by obesity and abdominal obesity. The findings, in addition to the numerous barriers to PA, support the community's desire for school-based PA programming.