The origins of pfSense can be traced to the OpenBSD packet filter known as PF, which was incorporated into FreeBSD in 2001. As PF is limited to a command-line interface, several projects have been launched in order to provide a graphical interface for PF. m0n0wall, which was released in 2003, was the earliest attempt at such a project. pfSense began as a fork of the m0n0wall project.

Version 1.0 of pfSense was released on October 4, 2006. Version 2.0 was released on September 17, 2011. Version 2.1 was released on September 15, 2013, and Version 2.2 was released on January 23, 2015. Version 2.3, released on April 12, 2016, phased out support for legacy technologies such as the Point-to-Point Tunneling Protocol (PPTP), the Wireless Encryption Privacy (WEP) and Single DES, and also provided a facelift for the web GUI. 

Version 2.4, released on October 12, 2017, continues this trend of phasing out support for legacy technologies while also adding features and improving the web GUI. Support for 32-bit x86 architectures has been deprecated (security updates will continue for 32-bit systems, however, for at least a year after the release of 2.4), while support for Netgate Advanced RISC Machines (ARM) devices has been added. A new pfSense installer (based on FreeBSD's bsdinstall) has been incorporated into pfSense, and there is support for the ZFS filesystem, as well as the Unified Extensible Firmware Interface (UEFI). pfSense now supports OpenVPN 2.4.x, and as a result, features such as AES-GCM ciphers can be utilized. In addition, pfSense now supports multiple languages; the web GUI has been translated into 13 different languages. At the time of writing, version 2.4.2, released on November 21, 2017, is the most recent version.