Context. Spirulina platensis (SP) has been found to be an important dietary supplement for boosting animal growth performance, having a high protein content (60-70% on a dry-matter basis) with minimal toxicity. Aims. The effect of Spirulina platensis (SP) supplementation on the growth and performance of two Omani goat breeds (Jabbali and Sahrawi) was investigated. Methods. Thirty-six 11-month-old bucks from two Omani goat breeds were studied for 70 days at the Livestock Research Centre, Ministry of Agriculture, Fisheries and Water Resources, Oman. Each breed was divided into three groups (n = 6) and fed one of the following three rations: (1) control (CON): concentrate with 14% crude protein and 11.9% energy (MJ/kg DM); (2) Treatment 1 (T1): the same concentrate with 2 g/head.day SP; and(3) Treatment 2 (T2): the same concentrate with 4 g/head.day SP. Weekly growth, performance and body conformation data collected included live bodyweight (BWT), body condition score (BCS), average daily gain (ADG), chest girth (CG), wither height (WH) and body length (BL). Key results. The Jabbali breed had a higher feed conversion ratio for T1 and T2 than did the Sahrawi breed. During the trial, no differences in total DM intake were found between treatments for either breed. T1 and T2 SP supplementation levels significantly (P < 0.05) improved the BWT and ADG of the Sahrawi breed compared with the CON group. Analysis of all traits indicated a significant (P < 0.05) effect of feeding spirulina on all the studied traits except WH and BL. ANOVAs for fixed effects in this study (dam age and kid birth type, i.e. single, twin or triple) were not significant (P > 0.05) for any of the studied traits. However, the breed effect was highly significant (P < 0.001) on BWT, ADG, BCS and treatment effect was significant (P < 0.05) on CG traits. Conclusions. Spirulina platensis could be used as a supplement feed to improve growth, performance and morphological traits in Omani goat production. Feeding spirulina to kids led to increased growth, herd performance and buck selection facilitation at an earlier age. Implications. These findings will benefit Omani goat producers in managing productivity and product quality.