The Magpies were flying high during that campaign, finishing fifth in the Premier League.
Newcastle seemed set for a bright future under Alan Padrew.
The English manager took a talented but limited-on-paper squad and had them playing some of the best football in the league.
It netted them a place in the UEFA Europa League play-offs, but that success was short lived.
The club did not spend enough in the transfer market the following summer, and tumbled down the league table.
They were eventually relegated to the Championship at the end of the 2015/2016 season.
Asked if Newcastle could have done more to continue the success of the 2011/2012 season, Williamson toldTribalfootball: "I think possibly yeah (did not build on that success).
"You can look back and in hindsight with a crystal ball everyone might do a few different things. But yeah in terms of the football club, of course, it's notorious the fact that when a team does well in Europe they struggle the following year, and we didn't really invest in the squad itself and we really did struggle in terms of nearly getting relegated.
"I suppose on hindsight we would've found ourselves in a better situation if the club invested a little bit more into the squad, but it's football and you can only control what you can control so for the players its frustrating because you want the best players to give you the best chance of being successful but you're obviously governed by your employer and the nature of the business."
Despite the good times only being brief during those years, Williamson admits that he will never forget that 2011/2012 season and their fifth place finish in the Premier League.
The Gateshead player-manager said: "It certainly was (special).
"For me I can only speak personally but it was for me, it was the highlight of my career the very top that I've played and when we were there it was just an unbelievable experience.
"Playing at St. James' Park, which is one of my favourite stadiums, bar many really because of the energy, atmosphere and passion in the crowd. And when you've got the European nights and you've got big teams coming, Manchester United, Arsenal, Liverpool, things like that, those experiences are priceless