iMovie will allow you to import the following file formats: MPEG-2 and AVCHD from Camcorders, DV (standard definition) and HDV (high definition), MPEG-4, DV, and .MPG files stored in Mac. If you want to import iPod and iPhone video files .mp4 into imovie, you should convert iPod and iPhone video files .mp4 to iMovie support video formats. How do i import my video files
mp4 to imovie?
MP4 to iMovie Converter not only can
import mp4 to imovie on Mac OS X, but also can import WMV, MP4, MOV, M4V, AVI, FLV, 3GP, 3GPP, 3G2, MPG, VOB, MPEG, MPG, ASF, MOD, MKV, HD video (Convert ts, tp, trp, m2ts, mts for Mac), etc . into iMovie on Mac OS X. MP4 to iMovie Converter is the most powerful Mac Video Converter for you to import video on Mac OS X (Leopard supported). So you can simple import mp4 to imovie that just several clicks.
How to import .mp4 video files into imovie on mac os x?
Step 1: Download, install and run MP4 to iMovie Converter
iMovie import mp4 is easy and safe for you.
Step 2: Add .mp4 video files
Click the "Add files" button to import your mp4 files. This mp4 into imovie converter support batch conversion, so you can import multiple files at a time.

Step 3: Select output format: "MPEG-4 Movie (*mp4)"

Step 4: Convert
Click "Convert" button, it begins to convert your .mp4 files to imovie mp4 format.

Step 5: Importing convertion mp4 files to imovie
Launch iMovie, go to "file > import movies". Select the converted MP4 video then click "import".