Thin-walled members in structural systems are highly vulnerable to buckling instabilities including web crippling. Aluminium alloy members are more prone to this kind of failure due to their relatively low elastic moduli. As shown in the existing literature, limited research has been performed to investigate the web crippling failure of aluminium members. Therefore, this paper presents the details of an experimental investigation conducted to study the web crippling phenomenon of fastened (restrained flanges) aluminium lipped channel (ALC) sections. Two loading conditions of End-Two-Flange (ETF) and Interior-Two-Flange (ITF) were considered. Two series of 40 tests were performed using roll-formed aluminium alloy 5052 H36 specimens with different web slenderness and load bearing lengths. A comparison between the ultimate capacities of the web crippling tests and the predictions form the currently available design rules was performed. The results show that the current web crippling design rules are mostly unsafe and unreliable for fastened ALC sections. Thus, a modified equation is needed to closely and accurately estimate the web crippling strengths for fastened ALC sections under two-flange loading conditions. Furthermore, the influence of restrained flanges on the web crippling mechanism was discussed in detail. It was observed that fastening the flanges considerably strengthened the section web crippling capacity; hence a new prediction approach was developed to estimate the increase of the web crippling capacity due to flange restraining.