Health Secretary Alex Neil said more people than ever are coming to hospital as emergency admissions, blaming it on an ageing population.
Opposition parties said the decision reflects wider problems in the NHS.
The Scottish Government wants to reduce the number of A&E attendances but concedes that existing trends could lead to a 13.5% increase by 2020.
The investment, over three years, aims to change the way people are admitted to hospital, help them leave as soon as they are ready and improve links with other areas of healthcare so support is in place in the community.
Mr Neil said: "We are seeing more people than ever before coming to hospital as emergency admissions due to the ageing population.
"We also know that the majority of people who go to A&E don't need to be there and could get more appropriate treatment somewhere else, such as a minor injuries clinic.
"That's why we have looked at the whole system and developed this action plan to improve how quickly people are seen in our hospitals, who treats them and how quickly we can get them back on their feet at home.
"Emergency and urgent care is one of the great success stories of the NHS in Scotland, whether responding to the anxious concerns of parents about their child, looking after an elderly person who has had a fall, or dealing with a major traffic accident."
Health boards will increase the number of frontline staff and introduce more flexible hours, develop projects that offer options to be treated at home and offer separate facilities for minor injuries beside or close to emergency departments, the Government said.
Other plans include the appointment of more consultants in emergency medicine and increased specialist clinical staff.
Staff could be working more flexible hours in a plan to make sure services are available around the clock.
Dr Jason Long, chair of the College of Emergency Medicine Scotland, said: "This is an important initiative that will improve emergency medicine across Scotland and we welcome the opportunity to collaborate on this initiative."
Scottish Conservative health spokesman Jackson Carlaw said the Government has "spectacularly missed" its targets on A&E admissions.
"While additional investment is welcome to make life more bearable for patients at A&E, it should never have come to this," he said.
"If certain health boards had been up front about the problems they were facing hitting wider waiting times targets, this could have been addressed years ago, and many of the issues wouldn't have dripped down to A&E departments."
Scottish Liberal Democrat health spokesman Jim Hume said: "The Health Secretary has been in denial and is late to the party in realising that Scotland's A&E units are in crisis.
"After weeks of pressure to do something about the patients who were left to languish on trolleys in cold hospital corridors, it is a relief to finally see some plans. Now we need to see action."
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