Did Irenaeus condemn prayer to angels?

Yes, though advocates of the practice sometimes suggest otherwise by adding qualifiers Irenaeus didn't include. Let's look at a couple of relevant passages.

Before I get to those, though, I want to make some observations about the larger context. As I've documented elsewhere, the Biblical and early patristic evidence heavily favors the conclusion that praying only to God, not to saints or angels, was the mainstream practice down to the time of Irenaeus and beyond his day to some extent. And though Irenaeus explicitly and repeatedly refers to praying to God, he never advocates praying to saints or angels. Revelation 5:8 is often cited in support of prayer to the saints, but Irenaeus sees the prayers in that passage as directed to God (Against Heresies, 4:17:6-4:18:1). With those contextual factors in mind, let's move on to the two passages I referred to earlier.

Irenaeus wrote:

"Nor does she [the church] perform anything by means of angelic invocations, or by incantations, or by any other wicked curious art; but, directing her prayers to the Lord, who made all things, in a pure, sincere, and straightforward spirit, and calling upon the name of our Lord Jesus Christ, she has been accustomed to work miracles for the advantage of mankind, and not to lead them into error. If, therefore, the name of our Lord Jesus Christ even now confers benefits [upon men], and cures thoroughly and effectively all who anywhere believe on Him, but not that of Simon, or Menander, or Carpocrates, or of any other man whatever, it is manifest that, when He was made man, He held fellowship with His own creation, and did all things truly through the power of God, according to the will of the Father of all, as the prophets had foretold. But what these things were, shall be described in dealing with the proofs to be found in the prophetical writings." (Against Heresies, 2:32:5)

Irenaeus is focused on miracles in this context, but he's also addressing the gifts and activities of the church in general. (Read section 2:32:4 and however much else you want to read for more of the context.) Besides, even if he only had miracles in view, those who pray to angels often ask them for miracles (e.g., prayers to the archangel Raphael for healing). So, this passage in Irenaeus is relevant to the prayer practices of Catholics, Orthodox, and others who pray to angels.

An advocate of praying to angels could qualify Irenaeus' comments in a variety of ways. You could add one or more qualifiers to "angelic" or "invocations". It's sometimes suggested, for example, that Irenaeus was only referring to bad angels, not angels in general. But that's a qualifier that the text doesn't spell out. Anybody who wants us to think Irenaeus had that qualifier in mind bears the burden of proof. The more natural way of taking his comment is that he's referring to angels in general. It's also insufficient to respond by saying that he was only opposing angelic invocations by heretics. When the church fathers condemn abortion when writing against pagans, for example, we don't conclude that the fathers only opposed abortion if pagans did it or only opposed it if it was done in a pagan way. Since Irenaeus chose such broad terminology, "angelic invocations", anybody who wants us to think he only had a particular subcategory of angelic invocation in mind bears the burden of proof. Similarly, though it's sometimes claimed that the term "invocation" only refers to an effort to summon an angel to appear before you, which is differentiated from praying to an angel, anybody who wants us to think Irenaeus used such broad terminology to refer to that sort of subcategory of invocation bears the burden of proof. Irenaeus refers to invoking God elsewhere (e.g., Against Heresies, 2:6:2; Fragments, 34), and he isn't referring to summoning God to appear before us in those contexts. Why should we think he has that sort of narrower definition in mind here? In the same manner, if somebody wants us to think Irenaeus was only condemning a form of invocation that involves a belief that angels would answer prayers alone, without any dependence on God or acknowledgement of him, for example, that's a qualifier Irenaeus doesn't mention. You would need to make an argument for interpreting him that way. To sum up, the burden of proof is on the shoulders of anybody who wants us to think Irenaeus had one or more qualifiers in mind that reconcile his comments with praying to angels, despite his having used such broad terminology.

Furthermore, shortly after mentioning the invoking of angels, Irenaeus contrasts that practice with how the church is "directing her prayers to the Lord, who made all things, in a pure, sincere, and straightforward spirit, and calling upon the name of our Lord Jesus Christ". So, instead of contrasting an inappropriate way of invoking angels with an appropriate way of invoking them, he contrasts the invoking of angels with praying to God. He doesn't include angels and saints with God. He just mentions God, as a Protestant would.

This passage creates a double problem for the advocate of praying to angels. Not only does Irenaeus condemn the practice, but he also goes on to contrast it with the alternative of praying to God, without any mention of praying to angels or saints.

The issue isn't whether it's possible to reconcile this passage with prayer to angels if we add one or more qualifiers to the text. Rather, the issue, as in other contexts involving historical judgments, is what explanation makes the most sense, not what explanation is possible.

Here's the other passage in Irenaeus:

"As, therefore, He does not stand in need of these [services], yet does desire that we should render them for our own benefit, lest we be unfruitful; so did the Word give to the people that very precept as to the making of oblations, although He stood in no need of them, that they might learn to serve God: thus is it, therefore, also His will that we, too, should offer a gift at the altar, frequently and without intermission. The altar, then, is in heaven (for towards that place are our prayers and oblations directed); the temple likewise [is there], as John says in the Apocalypse, 'And the temple of God was opened:' the tabernacle also: 'For, behold,' He says, 'the tabernacle of God, in which He will dwell with men.'" (Against Heresies, 4:18:6)

The context is about serving God, such as offering him the incense of prayer (e.g., 4:17:6, referring to prayer as incense in Revelation 5:8). As before, you could add qualifiers to what Irenaeus said, but the issue is how to make the most sense of his comments, not merely what he possibly meant. For example, you could add a qualifier to Irenaeus' reference to prayer, to the effect that he only had a particular type of prayer in mind, a type involving the worship due to God alone, not all types of prayer. But anybody advocating such a qualified reading of the text would have to argue for it, not just assert it.

What's noteworthy in this passage isn't just that Irenaeus refers to prayer as something offered to God, like incense. It's also that he refers to prayer in general being directed to heaven. Though angels are often in heaven, they're often elsewhere. They're messengers who often are active on earth and in other places outside what's normally thought of as heaven. The focus on heaven makes the most sense if God is the only one we're praying to.