The present study investigates the formability of the Aluminium (Al1050)/Steel (SS304) bimetallic sandwich composite sheet. The formability was predicted by generating the forming limit diagram (FLD) by using the experimental approach. The recorded strain distribution in terms of major and minor strain by using the digital correlation method was utilised for the generation of FLD. The failure in the utilised Al1050/SS304 sandwich composite sheet for the deep drawing of the cup was detected by recording the thickness strain distribution by using a numerical and experimental approach. The calculated thickness strain distribution in the deep drawn Al1050/SS304 sandwich composite cup was integrated with the strain non-uniformity index (SNI) approach for identifying defects such as thinning and thickening. The contribution of the individual sandwiched metal sheet on such kind of defects was also explored. The results signify that the prediction of the formability and identification of defects such as tearing and wrinkling for the deep drawn Al1050/SS304 sandwich composite cup can be performed precisely. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.