Poor geometric accuracy of formed parts is one of the key drawbacks in incremental sheet forming (ISF) process. In present experimental study, ISF is combined with stretch forming (SF) to improve the accuracy of formed parts. Influence of process parameters namely preforming, preform tool radius, wall angle, and tool offset on the geometric accuracy of parts formed in ISF process is investigated. A hemispherical ended forming tool of stainless steel (SS-304) is used to form frustum of cones with wall angle from 30° to 70°. Experiments are designed according to Taguchi’s orthogonal array (OA). From the experimental results, it is found that there is considerable influence of wall angle, preforming, and tool offset on the geometric accuracy of formed part. As the wall angle increases, geometric error reduces considerably resulting in accurate part shapes. The results obtained in present study will certainly be helpful to improve geometric accuracy of sheet metal parts formed using ISF in industries. © Springer Nature Singapore Pte Ltd. 2019.