Nicodemus was a Pharisee (see The Pharisees) but was challenged by what Jesus said. He met Jesus secretly and asked him a genuine question about being born again (John 3: 1- 21).
He is mentioned by name on two other occasions. Firstly after the Pharisees had tried to arrest Jesus, he pointed out that they should not condemn anyone without a hearing. (John 7:45-52). Secondly he is mentioned with Joseph of Arimathea after Jesus’ death when they asked for his body for burial (John 19:38-42).
It is also very likely that Nicodemus would have been present at the illegal night time trial of Jesus before Caiaphas the High Priest (Matthew 26:57-68).