“…Our prime contributions in this research are: the transfer learning strategy was exploited with the help of CNN’s pre-trained networks for feature selection and feature fusion [ 2 , 16 , 17 , 18 ]; the advantages of visual geometry group network (VGG16), EfficientNet B0, and residual neural network (ResNet50) such as low number of parameters and small size filters, multi objective neural architecture optimizing the accuracy and floating point operations with a balanced depth, width, and resolution producing a scalable, accurate and easily deployable model; and the ability to solve the problem of vanishing gradients of those three pre-trained networks have been explored deeply while designing this deep feature fusion model [ 12 , 13 , 14 , 15 ]. The key advantages of the ensemble learning mechanism to design a robust feature selection model by proposing combined feature fusion strategies [ 19 , 20 , 21 ], such as combined feature set (CFS), adaptive weighted feature set (AWFS), model-based optimized weighted feature set (MOWFS), and feature-based optimized weighted feature set (FOWFS), are experimented and validated. In order to reduce the losses and selection of optimized weights of those three pre-trained networks, the advantages of a new meta-heuristic optimizer artificial jellyfish optimizer (AJS) [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] was used and finally, the performance of the proposed feature fusion strategies are likened to other combinations of the models with genetic algorithm (GA) [ 30 ] and particle swarm optimization (PSO) [ 31 ] such as MOWFA-GA, MOWFS-PSO, FOWFS-GA, and FOWPS-PSO, and it was observed that the proposed combination of FOWFS-AJS outperforms the other models used for classification of skin lesion diagnosis.…”