MPs are to be given a £20m increase in their staffing budgets to help deal with "challenging" casework, including constituents with mental health issues.
The UK's 650 MPs will each receive more than £25,000 extra towards their staffing costs, with cash specifically for training, welfare and security.
It follows a review which suggested MPs' staff were underpaid compared with equivalent workers in other sectors.
Commons Speaker Lindsay Hoyle said his own staff were "struggling to cope".
The £19.7m increase - equivalent to a 13% year-on-year rise in staffing budgets - was approved by a committee headed by the Speaker on Tuesday.
It follows a campaign by more than 200 MPs last year for their staff to get a pay rise.
A report commissioned by the Independent Parliamentary Standards Authority (IPSA), the watchdog which oversee MPs' salaries and expenses, found that the job descriptions of those working for MPs did not "sufficiently match" the actual work they were doing.
It concluded that many of the 3,500 staff employed by MPs were increasingly "dealing with complex and challenging constituency cases" while also managing their offices - necessitating long, unsociable hours.
Staff were often having to support constituents with mental health issues, sometimes at risk to their own safety, while not being properly equipped to do so.
The new measures will mean each of the 650 MPs getting a staffing budget increase of £21,900 in London and £21,600 outside the capital. An additional £4,000 has been added to each budget to fund training, health and welfare costs.
"Bearing in mind the growing number of complex cases that are brought to our constituency offices, it's important staff are paid fairly for the vital job they do," said Sir Lindsay, who represents the Lancashire seat of Chorley.
"My own staff regularly have to help distressed constituents who are suicidal, fleeing domestic violence, have suffered rape, are homeless, need referrals to food banks, have the bailiffs banging at their doors, and are struggling to cope."
IPSA's interim chair Richard Lloyd said MPs' offices were having to deal with "difficult and stressful casework" with "relatively little time or money spent on training, wellbeing and development".
"We have provided additional funding in MPs' 2020-21 staffing budgets for staff training and welfare, security, and changes to the salary bands and job descriptions for MPs' staff to bring them into line with the jobs they actually do," he said.