That depends on which one you mean.
There are 5 men named James in the New Testament. Below is an article from Nelson's New Illustrated Bible Dictionary identifying each of these men:
1. James, the son of Zebedee, one of Jesus' twelve apostles. James' father was a fisherman; his mother, Salome, often cared for Jesus' daily needs (Mat_27:56; Mar_15:40-41). In lists of the twelve apostles, James and his brother John always form a group of four with two other brothers, Peter and Andrew. The four were fishermen on the Sea of Galilee. Their call to follow Jesus is the first recorded event after the beginning of Jesus' public ministry (Mat_4:18-22; Mar_1:16-20).
James is never mentioned apart from his brother John in the New Testament, even at his death (Act_12:2). When the brothers are mentioned, James is always mentioned first, probably because he was the older. After the Resurrection, however, John became the more prominent, probably because of his association with Peter (Act_3:1; Act_8:14). James was killed by Herod Agrippa I, the grandson of Herod the Great, sometime between A.D. 42-44. He was the first of the twelve apostles to be put to death and the only one whose martyrdom is mentioned in the New Testament (Act_12:2).
James and John must have contributed a spirited and headstrong element to Jesus' band of followers, because Jesus nicknamed them “Sons of Thunder” (Mar_3:17). On one occasion (Luk_9:51-56), when a Samaritan village refused to accept Jesus, the two asked Jesus to call down fire in revenge, as Elijah had done (2Ki_1:10, 2Ki_1:12). On another occasion, they earned the anger of their fellow disciples by asking if they could sit on Jesus' right and left hands in glory (Mat_20:20-28; Mar_10:35-45).
James was one of three disciples—Peter, James, and John—whom Jesus took along privately on three special occasions. The three accompanied Him when He healed the daughter of Jairus (Mar_5:37; Luk_8:51); they witnessed His transfiguration (Mat_17:1; Mar_9:2; Luk_9:28); and they were also with Him in His agony in Gethsemane (Mat_26:37; Mar_14:33).
2. James, the son of Alphaeus. This James was also one of the twelve apostles. In each list of the apostles he is mentioned in ninth position (Mat_10:3; Mar_3:18; Luk_6:15; Act_1:13).
3. James the Less. This James is called the son of Mary (not the mother of Jesus), and the brother of Joses (Mat_27:56; Mar_16:1; Luk_24:10). Mar_15:40 refers to him as “James the Less.” The Greek word mikros can mean either “small” or “less.” It could, therefore, mean James the smaller (in size), or younger (NIV), or James the less (well-known).
4. James, the father of Judas. Two passages in the New Testament refer to a James, the father of Judas (Luk_6:16; Act_1:13). Judas was one of the twelve apostles; he was the last to be listed before his more infamous namesake, Judas Iscariot.
5. James, the brother of Jesus. James is first mentioned as the oldest of Jesus' four younger brothers (Mat_13:55; Mar_6:3).
In the third and fourth centuries A.D., when the idea of the perpetual virginity of Mary gained ground, a number of church fathers argued that James was either a stepbrother to Jesus (by a former marriage of Joseph) or a cousin. But both options are forced. The New Testament seems to indicate that Mary and Joseph bore children after Jesus (Mat_1:25; Mat_12:47; Luk_2:7; Joh_2:12; Act_1:14), and that the second oldest was James (Mat_13:55-56; Mar_6:3). The Gospels reveal that Jesus' family adopted a skeptical attitude toward His ministry (Mat_12:46-50; Mar_3:31-35; Luk_8:19-21; Joh_7:5). James apparently held the same attitude, because his name appears in no lists of the apostles, nor is he mentioned elsewhere in the Gospels.
After Jesus' crucifixion, however, James became a believer. Paul indicated that James was a witness to the resurrection of Jesus (1Co_15:7). He called James an apostle (Gal_1:19), though like himself, not one of the original Twelve (1Co_15:5, 1Co_15:7).
In the Book of Acts, James emerges as the leader of the church in Jerusalem. His brothers also became believers and undertook missionary travels (1Co_9:5). But James considered it his calling to oversee the church in Jerusalem (Gal_2:9). He advocated respect for the Jewish law (Act_21:18-25), but he did not use it as a weapon against Gentiles. Paul indicated that James endorsed his ministry to the Gentiles (Gal_2:1-10).
The decree of the Council of Jerusalem (Act_15:12-21) cleared the way for Christianity to become a universal religion. Gentiles were asked only “to abstain from things polluted by idols, from sexual immorality, from things strangled, and from blood” (Act_15:20). The intent of this decree was practical rather than theological. It asked the Gentiles to observe certain practices that otherwise would offend their Jewish brothers in the Lord and jeopardize Christian fellowship with them.
Both Paul and Acts portray a James who was personally devoted to Jewish tradition but flexible enough to modify it to admit non-Jews into Christian fellowship. This James is probably the author of the Epistle of James in the New Testament.
I hope you have found this helpful.