Asklöf won three silver and one gold medals at the Junior World Championships in 1991 and 1992. In 1993 she won the silver medal with the Finnish women's relay at both the World Championships and the Nordic Championships. In 1995 she won the title at the Nordic Championships with Anniina Paronen , Marika Mikkola and her sister Kirsi Tiira in the second Finnish season . In 1997 the Finns defended this title with Asklöf in the relay. In addition, Johanna Asklöf won the title on the short distance and behind the Swiss Sabrina Meister-Fesseler the silver medal on the long distance. In 1998 she finished the World Cup season in second place behind the Norwegian Hanne Staff .
At the 1999 World Championships in Scotland, Asklöf was third on the long distance behind her sister and Hanne Staff. In the season she was running second. Asklöf played their last world championships in 2001 in Tampere, Finland . On the individual routes she was sixth and fifth as well as second behind Vroni König-Salmi in the newly introduced sprint competition. The Finnish relay finally achieved a clear home win with Reeta Kolkkala , Liisa Anttila , Marika Mikkola and the final runner Asklöf ahead of the Sweden and Norway seasons.