We introduce PokéLLMon, the first LLM-embodied agent that achieves human-parity performance in tactic battle games. It incorporates three key strategies: 1) In-context reinforcement learning that consumes text described feedback instantly derived from battles to iteratively refine its generation policy; 2) Knowledge-augmented generation that employs external knowledge to counteract hallucination and enables the agent to act timely and properly; 3) Action generation with self-consistency to mitigate the panic switching phenomenon when the agent faces a powerful opponent and want to avoid the battle. Online battle against human players demonstrate PokéLLMon's human-level battle performance and strategies, achieving 49% of wining rate in the ladder competitions and 56% of wining rate in the invited battles. In addition, we unveil its vulnerabilities to human players' attrition strategies and deception tricks.