Food production must increase markedly to feed the growing human population, but this needs to be achieved whilst simultaneously reducing adverse environmental impacts. In this regard, there is increasing interest in the use of nanomaterials as fertilizers for improving plant mineral nutrition. In the present review, we examine the ability of nanomaterials to supply a range of nutrients, with most focus given to recent research on phosphorus (P) and zinc (Zn). Some studies have demonstrated that nanomaterials can indeed be more effective than conventional fertilizers, especially by acting as a slow release source. However, other studies have found that nanomaterials have the same effectiveness, or are even less effective, than conventional fertilizers. Thus, ongoing investigation is required to understand the conditions under which the use of nanomaterials increases efficiency. We also note that there are a comparatively large number of studies that claim that nanomaterials are effective fertilizers despite not including appropriate control treatments in their experimental design. Furthermore, and of particular concern, a surprising number of studies conclude that nanomaterials are effective fertilizers despite their own analyses showing that the improvement in plant growth was not statistically significant. Overall, it is clear that nanomaterials are most likely to be effective where they can be tailored to act as a slow release source that improves nutrient use efficiency whilst simultaneously reducing adverse environmental impacts.