I believe so.
Popular thought on the subject agree that Bartholomew and Nathanael are the same person. While there is no passage in the Bible that directly says "Bartholomew is Nathanael," circumstantial evidence points in that direction. Arguments can be made either way; church tradition points toward them being one and the same.
First, regarding the names themselves. Bartholomew seems like a family name or last name. In Hebrew, the name would be Bar-Tholmai, or Son of Tholmai. Nathanael seems like a first name, meaning Gift of God.
Second, Bartholomew and Nathanael seem to be mutually exclusive. Bartholomew makes appearances in Matthew, Mark, Luke, and Acts. Each reference is in a list of the 12 Disciples. Nathanael makes appearances in the book of John, which has no formal list of the 12 Disciples. In John chapter 21, Nathanael is included in a list of disciples (
John 21:2 "There were together Simon Peter, and Thomas called Didymus, and Nathanael of Cana in Galilee, and the sons of Zebedee, and two other of his disciples.") In John, Nathanael does what one of the 12 Disciples might be expected to do: he goes fishing with some of the others in the 12 Disciples.
Third, there is a relationship between Philip and Bartholomew in the lists of disciples in Matthew, Mark, Luke, and Acts. There is also a relationship between Philip and Nathanael in John (Nathanael is the friend Philip brings to Jesus when Philip first learns of Him).
First, Bartholomew is a perfectly reasonable first name. It has been used many times since.
Second, Nathanael is never listed in a formal list of the 12 Disciples. Certainly, there were many disciples of Jesus who are not included in the 12 Disciples. This was one of the requirements to be considered for Judas' replacement in the 12 Disciples after Judas betrayed Jesus.
Third, the link between Philip and Bartholomew in Matthew, Mark, Luke, and Acts is hardly strong -- their names are simply grouped together. Even if the link were strong, it's not as if Philip cannot have two good friends.
The truth is that the Biblical authors were not concerned over whether we, thousands of years later, would definitively be able to link Nathanael and Bartholomew together. If they were, Matthew 10:3 would have read, "Philip, and Nathanael Bartholomew; Thomas, and Matthew the publican; James the son of Alphaeus, and Lebbaeus, whose surname was Thaddaeus;" (bold text added).