Categorization – whether of objects, ideas, or events – is a cognitive process that is essential for human thinking, reasoning, and making sense of everyday experiences. Categorization abilities are typically measured by the Wechsler Adult Intelligence Scale (WAIS) similarity subtest, which consists of naming the shared category of two items (e.g., ‘How are beer and coffee alike’). Previous studies show that categorization, as measured by similarity tasks, requires executive control functions. However, other theories and studies indicate that semantic memory is organized into taxonomic and thematic categories that can be activated implicitly in semantic priming tasks. To explore whether categories can be primed during a similarity task, we developed a double semantic priming paradigm. We measured the priming effect of two primes on a target word that was taxonomically or thematically related to both primes (double priming) or only one of them (single priming). Our results show a larger and additive priming effect in the double priming condition compared to the single priming condition, as measured by both response times and, more consistently, event-related potentials. Our results support the view that taxonomic and thematic categorization can occur during a double priming task and contribute to improving our knowledge on the organization of semantic memory into categories. These findings show how abstract categories can be activated, which likely shapes the way we think and interact with our environment. Our study also provides a new cognitive tool that could be useful to understand the categorization difficulties of neurological patients.