Should work, make sure to put deltaX and deltaY in math.rad() as CFrame.Angles() requires radians, and also so the numbers will be proportional to the mouse movement.
Edit:
RunService.RenderStepped:Connect(function()
UserInputService.MouseBehavior = Enum.MouseBehavior.LockCenter
local deltaX = UserInputService:GetMouseDelta().X
local deltaY = UserInputService:GetMouseDelta().Y
Camera.CFrame = Camera.CFrame * CFrame.Angles(math.rad(deltaX), math.rad(deltaY), 0)
end)