This paper examines compensatory lengthening (henceforth CL) in child Hijazi Arabic within the framework of prosodic theory and moraic theory to see if children acquiring Arabic use CL in case of coda/vowel deletion. On the basis of cross-sectional and semi-longitudinal data collected from 20 children aged from 1;3 to 2;0, the study describes and analyzes two CL types, V-lengthening and C-lengthening, providing a mora-based analysis and examining adjacency and directionality factors. The study provides cross-linguistic evidence for the existence of CL in child Arabic. The subjects use CL early (1;3) and arguably follow a universal path in this respect. Their productions display moraic conservation, sensitivity to bimoraicity and word minimality. They also show a preference for left-to-right directionality in CL.