This happened to me after installing the ttf-mscorefonts-installer package. I tinkered a bit and now Nautilus looks right again (it's back to using the Ubuntu font, as it normally does in Ubuntu).

Here is my procedure:

1) I opened a terminal and executed this fontconfig command:

$ fc-cache -rv

2) After the command finished, I logged out and logged back in.

I found other helpful font information in these questions:

Firefox fonts changed after install ttf-mscorefonts (This is what convinced me there may be problems installing the ttf-mscorefonts-installer package.)

Can I override fonts installed by ttf-mscorefonts-installer, prefer Liberation fonts? (This is where I got the idea of trying a fontconfig command.)

UPDATE: As I mentioned in the comment below, I decided the ttf-mscorefonts-installer causes problems in recent versions of Ubuntu, so I removed it. Nowadays LibreOffice includes the Liberation fonts, which are metrically-compatible with three of the common fonts:

• Liberation Serif: same metrics as Times New Roman


• Liberation Sans: same metrics as Arial


• Liberation Mono: same metrics as Courier

If you don't use LibreOffice, you can get the fonts above by installing fonts-liberation package.

You can also match some other common Microsoft fonts:

• Carlito: same metrics as Calibri


• Caladea: same metrics as Cambria

The two fonts above are available by installing the fonts-crosextra-carlito and fonts-crosextra-caladea packages.

If you need a font compatible with Impact, Verdana, Trebuchet or Webdings, unfortunately I don't have a suggestion at this time.