I recently installed SourceTree on a new Win10 laptop and noticed SourceTree wasn't using my global .gitignore file. I wasted a couple hours trying to get it working. It looks like a bug under the options page. The first item at the top of the page is "allow SourceTree to modify your global Git config files" and I verified that this was enabled but I noticed that when I changed the path for the "Global Ignore List" in the SourceTree options that my "c:\users\ssmith\.gitconfig" didn't have the updated excludesfile path. It was still listed as "~/.gitignore". After trying a bunch of different ideas, I finally unchecked the "allow SourceTree to modify your global Git config files" option, restarted SourceTree, then checked it again. And then I set the path for the "Global Ignore List" in the SourceTreeoptions again. After that, my global .gitignore started working. Also, I noticed that the excludesfile path in my "c:\users\ssmith\.gitconfig" was now set to "C:\\Users\\ssmith\\.gitignore" instead of "~/.gitignore". So in summary, it looks like SourceTree might not be correctly reading the "allow SourceTree to modify your global Git config files" option. So unchecking it and checking it again might signal SourceTree that you really, really want to enable this option.