When the Wei regent Sima Zhao ordered the generals Zhong Hui and Deng Ai to attack Wei's rival state Shu Han in 263, Wei Guan served as Deng Ai's deputy. After the fall of Shu that year, Zhong Hui planned a rebellion, and the first step of his preparation was to falsely accuse Deng Ai of treason. Sima Zhao, believing Zhong Hui's accusations, ordered Deng Ai arrested, and Zhong Hui in turn ordered Wei Guan to arrest Deng Ai, hoping that Wei Guan would fail and be killed by Deng Ai so that he could further affirm his accusations against Deng Ai. Wei Guan knew this, so he surprised Deng Ai in the middle of the night and arrested him. When Zhong Hui rebelled later, Wei Guan pretended to be seriously ill, so Zhong Hui lowered his guard against Wei Guan. Later, Wei Guan participated in inciting the soldiers to start a mutiny against Zhong Hui and end the rebellion. Fearful that Deng Ai would then retaliate against him, he had Deng Ai tracked down and killed. When Du Yu publicly denounced Wei Guan, instead of becoming angry and retaliate against Du Yu, Wei Guan visited him and apologised. He also declined a larger fief that Sima Zhao was ready to bestow on him for his accomplishments.