In 451 Pericles introduced a new citizenship law which prevented the son of an Athenian father and a non-Athenian mother becoming a full citizen. The law's main effect was to curb the power of the aristocrats since if their heirs could not be legally recognized they could no longer forge alliances with aristocrats from other cities. Ironically, it would have major consequences for Pericles own private life.

A few years later Pericles divorced his wife and started to live with a beautiful foreign courtesan called Aspasia, described by Socrates as one of the most intelligent and witty women of her time. The relationship scandalized polite society, especially because they remained unmarried and Pericles treated her as an equal, an almost unthinkable action for most Greek men.

But though Pericles became the butt of vicious jokes about his private life, in public office he was known for his incorruptibility and refusal to accept gifts from other aristocrats, as was the normal custom. Instead he kept to himself, limiting his public appearances before the assembly, but slowly coming to dominate it with his aristocratic style and superb oratory skills.