However, he stressed the need for more data in order to be definitive.
On Thursday, the Scottish Government's daily coronavirus figures included both PCR and lateral flow test numbers for the first time.
This was due to a change in the rules where a positive lateral flow result no longer needed a PCR confirmation.
Mr Yousaf appeared on the BBC's Good Morning Scotland radio programme on Friday, where he was asked if the Omicron wave had passed its peak.
The Health Secretary said he had spoken to his clinical advisors about it yesterday, saying: "A few more days of data would be extremely helpful to give a definitive answer to that.
"But I think it would be safe to say at this stage that the Omicron wave is decelerating.
"That is evident if you look at hospital numbers, where hospital admissions, although they continue to increase, there's definitely a slowing-down of the rate of the increase.
"Certainly, the case numbers themselves, notwithstanding the instability of some of the data because of the recent changes, certainly looks like those numbers are lower than where we were at the peak."
It would be necessary to wait a little longer to see the impact of schools returning, he said.
The Health Secretary also spoke about the recent decision to cut the self-isolation period for some positive cases, subject to two consecutive negative lateral flow tests.
He said: "The First Minister herself has said that when we made these self-isolation changes, it's not that they were risk-free.
"They have an element of risk."