How to report a mixed ANOVA in APA format

A mixed ANOVA has a within-subjects factor and a between-subjects factor, so there are three effects to report: two main effects and the interaction.

Report the interaction first

If the interaction is significant, it changes how the main effects should be read, so deal with it before them.

There was a significant interaction between time and treatment group, F(1.72, 65.44) = 8.91, p < .001, ηp² = .19.

Then the main effects, with the caveat

There was a significant main effect of time, F(1.72, 65.44) = 22.30, p < .001, ηp² = .37, and a significant main effect of group, F(1, 38) = 5.12, p = .029, ηp² = .12. These main effects should be interpreted in light of the significant interaction.

That final sentence matters. See significant interaction in a two-way ANOVA.

Sphericity

Fractional degrees of freedom mean a correction has been applied. Say which:

Where Mauchly's test indicated a violation of sphericity, Greenhouse-Geisser corrected degrees of freedom are reported.

Sphericity applies only to within-subjects factors with three or more levels. See Mauchly's test.

Follow-up

With a significant interaction, report simple effects: the effect of time within each group, or of group at each time point. Name the correction you applied.

Effect sizes

Partial eta squared is conventional for ANOVA. Report it for every effect, significant or not.

Also state

Sample size per group, that listwise deletion was used and how many cases it removed, and the homogeneity of variance check for the between-subjects factor.

In Plotara

Mixed ANOVA with per-effect Greenhouse-Geisser correction, and a Methods panel that writes these sentences with your numbers.