Though he is most well-known for his doubts about the resurrection, Thomas appears more times in the New Testament than most of the other Apostles. John records many of the doubting Apostles’ thoughts and feelings about the events of the New Testament.
(See his full biography here: Who was Thomas the Apostle?)
Thomas in Acts
12 Then the apostles returned to Jerusalem from the hill called the Mount of Olives, a Sabbath day’s walk from the city. 13 When they arrived, they went upstairs to the room where they were staying. Those present were Peter, John, James and Andrew; Philip and Thomas, Bartholomew and Matthew; James son of Alphaeus and Simon the Zealot, and Judas son of James. 14 They all joined together constantly in prayer, along with the women and Mary the mother of Jesus, and with his brothers.
Acts 1:12-14
Thomas in John
11 After he had said this, he went on to tell them, “Our friend Lazarus has fallen asleep; but I am going there to wake him up.” 12 His disciples replied, “Lord, if he sleeps, he will get better.” 13 Jesus had been speaking of his death, but his disciples thought he meant natural sleep. 14 So then he told them plainly, “Lazarus is dead, 15 and for your sake I am glad I was not there, so that you may believe. But let us go to him.” 16 Then Thomas said to the rest of the disciples, “Let us also go, that we may die with him.”
John 11:11-16
24 Now Thomas (also known as Didymus), one of the Twelve, was not with the disciples when Jesus came. 25 So the other disciples told him, “We have seen the Lord!” But he said to them, “Unless I see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, I will not believe.”
26 A week later his disciples were in the house again, and Thomas was with them. Though the doors were locked, Jesus came and stood among them and said, “Peace be with you!” 27 Then he said to Thomas, “Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe.” 28 Thomas said to him, “My Lord and my God!” 29 Then Jesus told him, “Because you have seen me, you have believed; blessed are those who have not seen and yet have believed.”
John 20:24-29
Afterward Jesus appeared again to his disciples, by the Sea of Galilee. It happened this way: 2 Simon Peter, Thomas (also known as Didymus), Nathanael from Cana in Galilee, the sons of Zebedee, and two other disciples were together.
John 21:1-2
Verses in Matthew, Mark, and Luke
1Jesus called his twelve disciples to him and gave them authority to drive out impure spirits and to heal every disease and sickness. 2 These are the names of the twelve apostles: first, Simon (who is called Peter) and his brother Andrew; James son of Zebedee, and his brother John; 3 Philip and Bartholomew; Thomas and Matthew the tax collector; James son of Alphaeus, and Thaddaeus; 4 Simon the Zealot and Judas Iscariot, who betrayed him.
Matthew 10:1-4
13 Jesus went up on a mountainside and called to him those he wanted, and they came to him. 14 He appointed twelve that they might be with him and that he might send them out to preach 15 and to have authority to drive out demons. 16 These are the twelve he appointed: Simon (to whom he gave the name Peter), 17 James son of Zebedee and his brother John (to them he gave the name Boanerges, which means “sons of thunder”), 18 Andrew, Philip, Bartholomew, Matthew, Thomas, James son of Alphaeus, Thaddaeus, Simon the Zealot 19 and Judas Iscariot, who betrayed him.
Mark 3:13-19
12 One of those days Jesus went out to a mountainside to pray, and spent the night praying to God. 13 When morning came, he called his disciples to him and chose twelve of them, whom he also designated apostles: 14 Simon (whom he named Peter), his brother Andrew, James, John, Philip, Bartholomew, 15 Matthew, Thomas, James son of Alphaeus, Simon who was called the Zealot, 16 Judas son of James, and Judas Iscariot, who became a traitor.
Luke 6:12-16