There are multiple aspects of this question to look at, and I spent quite a bit of time with this question as I worked on the Unseen Dominion series. At first glance Jesus’ response to a question by the Sadducees (a religious group that didn’t believe in either the resurrection or the existence of angels) seems to address this question. Some Sadducees made up this funky scenario about a woman who was successively married to seven brothers, each after the prior brother’s death. Then they asked Jesus whose wife she would be in the resurrection. Here is Jesus’ response.
Jesus told them, "Are you not deceived because you don't know the Scriptures or the power of God? For when they rise from the dead, they neither marry nor are given in marriage but are like angels in heaven. (Mark 12:24-25)
Jesus response goes directly to the heart of the Sadducees’ misbeliefs. When they rise from the dead—of course there is a resurrection. And, they are like angels in heaven—yes they exist. There is also an aspect of their disbelief in a final judgement that He addresses (Luke 20:34-36). But does Jesus answer our question about angel gender?
Not really. We can read this to instruct that angels do not marry. This does not, however, indicate that they are genderless, any more than we would interpret that people will no longer have gender in heaven. In fact, the wording neither marry nor are given in marriage reflects both genders, as this would have been viewed as men marrying, and women being given in marriage.
Beyond this passage, we are told very little about angels in regards to gender. All of the passages in the Bible that refer to angels use the masculine form (with the possible exception of Zechariah 5:9, which some believe refer to angels, though this is uncertain). Also, the three named angels in the Bible are masculine names: Gabriel, Michael, and Lucifer (also known as Satan after his fall). However, we are never told that all angels are masculine.
In reality, we know almost nothing about the gender of angels. Angels are a unique creation, totally separate from humans and thus most descriptions of their appearance are more of a projection of humanity on them. This is why I felt the creative freedom to include angels that are feminine, at least in appearance. This was especially true in Restoration’s Journey where a feminine guardian of a young pre-teen felt more appropriate and maternal.
Here is one of many scenes that deals with this topic, from Restoration’s Journey.
The demon smiled. “Ah yes, you remember.” The demon took a couple steps toward Adiya and then rested his hand gently on the hilt of his saber. “For old times’ sake, we will let you leave now. Without messing up that pretty little face of yours.”
Though neither angels nor demons possess gender as humans do, it always fell to the demons of lust to draw attention to Adiya’s feminine form. “For too long you have hung out with this human, if you believe my appearance makes me any less of a warrior.” More memories of worshiping next to this former angel of heaven flooded her mind. How could anyone who experienced the loving presence of the Creator ever rebel against Him? – Restoration’s Journey