Alias defined in .bash_profile not working in OS X

Assuming:

• you use OS X's native terminal, Terminal.app, or popular alternative iTerm2
• and bash is indeed your shell (as is the default on OS X)

then ~/.bash_profile should be loaded for every interactive shell, because both terminal programs create login shells by default.
Bash login shells source ~/.bash_profile, but not ~/.bashrc.

^{Note that this differs from most Linux distros, where a single login shell is executed on startup, and later interactive shells are non-login shells, which only load ~/.bashrc, not ~/.bash_profile.
A frequently seen technique to ensure that definitions are loaded in both login and non-login interactive shells is to place definitions in ~/.bashrc, and then source it from ~/.bash_profile, using the following line:
[[ -f ~/.bashrc ]] && . ~/.bashrc}

You can create a login shell on demand by executing bash -l from an existing shell; if that loads your aliases, then the problem must be with what your default shell is and/or how your terminal program is configured.

• echo $SHELL tells you what your default shell is.
• if you use Terminal.app, Terminal > Preferences..., tab General, setting Shells open with tells you whether the default shell or a custom shell is being used.

We still don't know why aliases are not loaded automatically.

Your aliases should be loaded from the .bash_profile. This is the default behaviour of bash in OS X.

mklement0 wrote more about the problem in their answer in this thread.

A hacky workaround

Open the Preferences of the Terminal. You specify the command you start your shell with:

Instead of manually sourcing your dotfiles every time you can specify which file you want to source when the shell opens. Here is the list of options for bash:

Usage:  bash [GNU long option] [option] ...    bash [GNU long option] [option] script-file ...GNU long options:    --debug    --debugger    --dump-po-strings    --dump-strings    --help    --init-file    --login    --noediting    --noprofile    --norc    --posix    --protected    --rcfile    --restricted    --verbose    --version    --wordexpShell options:    -irsD or -c command or -O shopt_option      (invocation only)    -abefhkmnptuvxBCHP or -o option

You might consider using /bin/bash --rcfile alias_file_of_yours or something similar.

Go for goat if you need aliases using the cd command.

As a side note I do recommend you to check out goat. It lets you manage such cd aliases easily.

I use it and I wrote it.