The ex-Cardiff Blues duo have helped Wales win three Six Nations titles and reach the World Cup semi-finals in 2011 and quarter-finals in 2015.
"This is a team that works well together," said Welsh Rugby Union chief executive Martyn Phillips.
"It has trust."
Defence coach Shaun Edwards has also committed his future to Wales until the next World Cup in Japan.
"We have a clear focus and strategy in place and we will continue to work hard to give the players the very best opportunity to achieve their full potential," said Howley.
McBryde added: "We all feel we have some unfinished business at the Rugby World Cup and, as Martyn Phillips has identified, a successful trip to Japan is the key overreaching target for us all."
Wales are trailing their current series in New Zealand 2-0, with the remaining Test on Saturday.
Wales assistant coach Rob Howley and forwards coach Robin McBryde have agreed new deals to remain part of Warren Gatland's backroom team until after the 2019 World Cup.