The British Medical Association (BMA) Wales questioned GPs about their workload and work-life balance and plans to stay in post or not.
It said GPs had voiced serious concerns over the sustainability of practices, with more than 80% worried.
The Welsh Government said it was launching a major recruitment drive.
Last month, the BMA said a crisis facing GP services in some parts of Wales was getting worse, as figures suggested a spike in the number of practices being handed back to health boards to manage.
The BMA is launching a campaign, An urgent prescription for general practice in Wales, as the report is published.
The survey was sent to all its GPs in Wales and 244, or a fifth of those asked, responded, with a relatively even response rate across the country.
The BMA said it was "confident" the level of response would have delivered "representative results".
Of those, 65, or 27%, said they were considering a career change and nearly 14% (13) were planning to work abroad within the next 12 months.
Worries about understaffing were high up the list, with some practitioners considering reducing their working hours to cope with growing pressures.
More than 60% of respondents said they did not have a good work-life balance, with 58% saying that balance had worsened over the past year.
Three-quarters said the health of staff within their practice had already been negatively affected by the workload, and nearly half would not recommend a career in general practice.
Dr Charlotte Jones, chairwoman of BMA Wales' GP committee (GPC) said: "There is a significant gap between the demand placed upon general practice and its capacity.
"The profession is forced to try and cope with inadequate resources, an unsustainable workload and a workforce under considerable strain, across the whole of Wales.
"The survey findings have identified clear trends in GPs' areas of concern and highlights just how immediately action needs to be taken. GPs continue to remain committed to the profession but for it to turn around, they need the tools, resources and support of Welsh Government."
A Welsh Government spokeswoman said: "As the BMA are aware, we will be launching a major national and international recruitment campaign at the end of October to market Wales and NHS Wales as an attractive place for doctors, including GPs and their families, to train, work and live.
"We continue to invest in primary care and will shortly be entering into discussions with GPC Wales about changes to the General Medical Services Contract."
The report was released the same day as a conference on rural primary care is being held in Gregynog Hall, near Newtown, Powys, hosted by Montgomeryshire Medical Society, to discuss what it called a crisis in GP services in many rural parts of Wales and the UK.
Dr Michael Lewis, a Welshpool GP, said: "Recruitment campaigns have had little or no success, so together Powys Teaching Health Board and general practices are looking at new ways of providing primary care.
"This often depends on working with other healthcare professionals or new technology and has been vital in keeping practices open."
Future Generations Commissioner for Wales Sophie Howe said: "We are only too aware of the pressure on our health service and the people who work within it and we cannot continue to deliver services in the way that we have been.
"Some fundamental changes are needed to provide interventions outside the traditional medical treatment model which use services outside the NHS to deal with issues such as such obesity to mental health."

Almost 90 jobs were at risk after bus operator First Scotland East announced it was withdrawing services in East Lothian.
In May 2016, First Group revealed plans to stop bus operations in the area from 14 August 2016.
It also proposed closing its depots in North Berwick and Musselburgh.
The firm had blamed "an increasingly competitive market".
An agreement has now been reached which will see East Coast Buses Ltd, a wholly owned subsidiary of Lothian Buses Ltd, buy the Musselburgh and North Berwick depots with all staff having the option to be transferred.
The buyer has also announced plans to improve services and increase the number of vehicles.
Richard Hall, managing director of Lothian Buses, said: "We are pleased to be in a position to take on and continue providing these vital services and be part of the local economy."
Paul McGowan, managing director of First Scotland East Ltd, said: "I'd like to thank all my colleagues in East Lothian for their hard work and loyalty over the years."
He added: "We will be fully supporting them as they transfer to their new employer."
More than a quarter of GPs surveyed in Wales are considering leaving the profession, a report by a doctors' group has said.
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Threatened East Lothian bus services and jobs have been saved as part of a new takeover package from Lothian Buses Ltd.