The Moroccan financial market experienced a major modernization wave resulting in an increasing capitalization, a significant “volume & value” of business and a growing number of new IPOs in order to transform the Moroccan economy from a debt economy to a capital market economy and therefore achieve an optimal state of resources allocation. The informational efficiency of the Moroccan financial market has recently become a serious topic that arouses much interest among researchers and practitioners leading to an increasing number of studies in this area. The objective of our paper work is to investigate the weak form efficiency of the Moroccan stock market. We first remind what we mean by “market efficiency” and also the debate on this issue in developed and emerging markets, African markets and Morocco stock market. We then explain in depth the main Author α: Doctorant, Ecole Nationale des Sciences Appliquées (ENSA), Agadir, Maroc. Laboratoire de Génie Informatique et Industriel (L.G.I.I) Groupe de Recherche en Ingénierie de la Décision (G.R.I.D). e-mail: faycal [DOT] chiny [AT] gmail [DOT] com Author σ: Directeur du L.G.I.I, ENSA Agadir, Maroc. empirical tests of market efficiency: autocorrelations, unit root, variance ration and the runs test. The time series considered consist of daily data of four stock indexes: MASI (Moroccan All Shares Index), BNQ (Banking sector index), ASSUR (Insurance sector index) and IMMO (Real Estate sector index) from January 1st 2002 to December 31st 2013. The results of these various tests strongly reject the weak form efficiency hypothesis and an analysis of this inefficiency and its potential sources is given in conclusion that highlights causes that might be the origin to the markets dysfunction anomalies.