He studied with Bratt for three and a half years before joining the Opera School attached to the Royal Opera House in Stockholm. In 1914 he made he debut in the title role of Faust at the Royal Theatre. In the following six years he appeared in many leading roles across Sweden and Norway becoming Scandinavia's highest paid opera singer (he would later be knighted by both the kings of Sweden and Denmark for his services to Opera). He began to travel the world, singing in La Scala in Milan, Covent Garden in London, Paris and elsewhere in Europe. He toured the USA and Canada, South America, Australia and New Zealand. He sang in six different languages and made many recordings, including 150 records for HMV. When the great Caruso died in 1921, Hislop was tipped as a successor.

"Scotland's world famous tenor is appearing in person, supported by a brilliant company of international artistes. This is the first occasion on which Mr Joseph Hislop has made a comprehensive tour of his native land, and it says much for the influence of Kirkcaldy that the town has been included in My Hislop's itinerary. During the past few years, Joseph Hislop has sung in every great Opera House throughout the civilised world....It is expected that the capacity of the hall will be tested to its uttermost on the occasion of this outstanding event."
The tour left his voice strained and, soon afterwards, Hislop retired from performing and began to teach, initially in Stockholm at the Royal Academy of Music. One of his pupils was the soprano Birgit Nilsson. By 1947 he moved to London and advised at Covent Garden and Saddler's Wells, as well as teaching at the Guildhall School of Music. Joseph and his second wife Nancy eventually began to yearn for Scotland and in 1969 retired to Fife, settling in Berryside farmhouse south of New Gilston (a location chosen because Nancy had connections with Cupar and Joseph enjoyed golf - playing regularly at both Lundin Links and St Andrews). Joseph continued to teach privately from Berryside with some of his students staying in a caravan on the farm. In the book 'Joseph Hislop - Gran Tenore' by Michael Turnbull, the Scottish baritone Donald Maxwell recalls his regular visits of Berryside...
"I'll never forget driving up to the farmhouse and hearing him busily practising the day's scales, for he warmed up his voice rigorously even though over 90...My strongest memory is of sitting at Berryside on a summer's day looking over to Largo Law and discussing Scots songs....My last memory of him was about a couple of months before he died. We were sitting listening to the re-releases of some of his records. He was by then rather frail but typically, for a tenor, he smiled approvingly at his top note."
Joseph Hislop died peacefully at home in his sleep on 6 May 1977, aged 92, and was survived by his wife, son and two daughters. Examples of his singing can be found on-line:
https://www.youtube.com/watch?v=cFzgR--q-7s