Thursday's economic blueprint will include an additional $181 million for new and expanded programs with total spending across the sector rising by 13 per cent.
The new funds include $47.3 million to respond to recommendations of the Ministerial Taskforce into Public Mental Health Services for infants, children and adolescents in WA.
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The government will also provide $6.1 million to continue a range of prevention initiatives for foetal alcohol disorder and $3.5 million for suicide prevention services.
Health Minister Amber-Jade Sanderson said the government would reinforce its commitment to mental health, alcohol and other drug services in this year's budget.
"Improving the mental health outcomes for children and adolescents is an important area of focus and builds on record investment from the last budget," she said.
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"It's a priority for us to ensure people receive the mental health care they need, as demand for services across the country continues to increase.
"This will help address mental ill-health where it starts - in the early years of someone's life - which has the potential to positively impact their trajectory."
In other pre-budget announcements on Monday, the government said it would provide $12.6 million to preserve and enhance the World Heritage-listed Fremantle Prison.
The cash will cover critical maintenance and restoration works with the government to seek matching funds from the commonwealth.
Fremantle Prison, built by convicts in the 1850s and closed as a working jail in 1991, is the only World Heritage-listed building in WA.
Heritage Minister David Templeman said the tourist attraction was an important piece of the state's heritage as a unique reminder of WA's architectural, social and penal history.
"This iconic building is an important Fremantle landmark that demonstrates how conservation and tourism can align for community purpose and benefit," he said.