Learning disabilities in mathematics (in 1 to 10% of school children) cover a broad range of specific difficulties and represent a major handicap for academic achievement, social and professional integration. The response-to-intervention model is centred on the prevention of learning difficulties and the differentiation of remedial interventions. One component of this approach is the assessment of the mathematical skills. The aim of this article is to present a systematic approach to assess mathematical skills in order to highlight the child’s strengths and weaknesses and provide relevant information for guiding a remedial intervention. We present: 1) a short critical synthesis of the tools available to professionals for assessing mathematical skills and their psychometric properties; 2) an approach for the assessment of mathematical and cognitive skills; and 3) a case study.