Generally speaking, an associate/assistant pastor is a pastor who serves in a supporting role to a church’s senior pastor. Sometimes the role is somewhat of an internship, preparing the man to later serve as a senior pastor. Other times an associate/assistant pastor performs administrative responsibilities to free up the senior pastor to focus more on teaching, preaching, and discipleship. Although the specific words "associate pastor" or "assistant pastor" are not found in the Bible, Scripture does refer to elders, and it can be said that the associate and assistant pastors are elders, leaders in the church serving alongside the pastor, with Jesus as the Head of the church. That is the key for every person in leadership, to recognize that the church belongs to Christ, to recognize that He is the Head of the church (Ephesians 4:15), and to recognize that a leader is really a servant who has not come to be served, but to serve others.
Associate pastors and assistant pastors are to adhere to the same standards as senior pastors and other elders. Church leadership is described in 1 Timothy 3:1-13, but there are other verses that refer to the duties of elders and what is expected of them. For example, the elders bring order into the church: "For this cause left I you in Crete, that you should set in order the things that are wanting, and ordain elders in every city, as I had appointed you" (Titus 1:5, KJV). Also, the elders, especially those that teach, are to be supported by the ministry, if possible: "Let the elders that rule well be counted worthy of double honor, especially they who labor in the word and doctrine" (1 Timothy 5:17, KJV).
In addition, elders are to be examples to believers, feeding them with the good doctrine of the Word of God as they serve. And they are rewarded for their service. “The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed: Feed the flock of God which is among you, taking the oversight thereof, not by constraint, but willingly; not for filthy lucre, but of a ready mind; Neither as being lords over God’s heritage, but being ensamples to the flock. And when the chief Shepherd shall appear, you shall receive a crown of glory that fades not away” (1 Peter 5:1-4, KJV).
The elders also have a ministry of prayer, and prayer is, of course, important in any ministry. An example of the type of prayer pastors should offer up on behalf of their congregations is Jesus’ high priestly prayer in John 17:15-26, where He prays for all His disciples to be protected from the evil one, sanctified by the Word, and made perfect in Him. Although not specifically mentioned in Scripture, associate/assistant pastors are to be as other elders: strong in the Word of God, strong servants, and men of prayer.