jats:titleAbstract</jats:title>jats:pRecent findings have shown that even without the ability to customize a product, individuals pay more for goods that they assembled. In this paper we examine which components of this creation process account for the increase in valuation, and whether it operates equally for owners and non‐owners of the self‐assembled object. Based on the self‐extension theory of ownership, we propose a psychological mechanism by which the assembly process strengthens the self–object association. In three experiments, we find that—although witnessing the assembly process or assembling a similar product can increase participants' evaluation of, and attachment to, a product that they own—a greater and more consistent increase in valuation and attachment arises when owners assemble their product themselves. Seemingly, merely learning about the assembly process plays only a small role in enhancing value; for substantial increases in value, one must actually assemble the product oneself. Contrary to the previous findings on the effects of labour on willingness to pay, we find little effect of product assembly among non‐owners of the product. We suggest that self‐assembly encourages objects to be incorporated into the self, but that this occurs most effectively when one owns the product. Copyright © 2015 John Wiley & Sons, Ltd.</jats:p>