Life history theory predicts that parents will not raise unrelated offspring. For seabirds, an ability to recognize their own eggs and chicks can prevent a costly mistake. We tested whether Magellanic Penguins (Spheniscus magellanicus) would discriminate against artificial eggs by presenting nine types of egg-objects and one type of artificial chick to penguins at their nests. Magellanic Penguins regardless of their sex or breeding status accepted all egg-objects. A generalized linear mixed model showed that mass and number of dimensions were the most important factors in predicting whether the object was accepted: flat egg-objects and light egg-objects were less likely to be incubated than round, normally weighted ones. We also tested whether Magellanic Penguins would retrieve egg-objects more frequently if the object was within 1 m of the nest cup. Penguins retrieved 75 % of objects that were 1 m from the nest cup, but only 25 % of objects that were 2 m from the nest cup. Lastly, we tested whether penguins would accept artificial chicks. We found that pairs with chicks less than 3 weeks of age (i.e., not out of the guard stage) were at least twice as likely to brood an artificial chick than pairs with chicks older than 3 weeks, pairs that had lost their chicks, or unmated males.