The average age of membership applicants in the seven months since May fell from 37 to 29, the BCS said.
In the professional member grade the average age of new BCS entrants has dropped from 40 to 33. The average age for those entering the top membership grade of fellow has fallen from 58 to 43. At the lowest membership level of affiliate, the average age has dropped from 41 to 31.
Total membership has grown by more than 8,500, taking the total to about 45,000.
"The fall in the average age of members reflects our determination to appeal more broadly to young IT professionals as part of our membership recruitment campaign," said BCS chief executive David Clarke.
"In addition, our membership growth of more than 20% shows that we are bucking the diminishing membership trend seen in many other professional bodies.
"We are determined to ensure greater inclusion of the whole IT profession in the BCS. The profession has many new roles, competencies and experience. Bringing these new skills into BCS membership is critical to our plans to become the voice for the whole of the IT profession.
"Over the past 20 years IT has been one of the fastest-changing professions, driven by the continuous development in technology. Yet I believe the likely changes over the next decade will even outpace all previous ones.
"Several factors will drive this change, including globalisation of supply, with the move of some activities to cheaper markets, but mostly a growing awareness that IT does not work in its own discrete world," said Clarke.
"For IT-enabled projects to be successful, the IT profession will need to become more integral to the markets it is serving.
"Future skill requirements are going to be about the application of technology rather than simply the writing of programming code.
"Only those professionals who understand the need to develop their skills in entirely new areas will score true successes.
"These changes to the skills of IT professionals will also underpin a revolution in the success rates of IT-enabled projects. IT professionals with these skills will be more successful and so will the businesses they work for.
"Although most IT professionals will have to take their career development into their own hands, the BCS understands its key role in helping its members and the wider IT profession achieve these career path changes."
The revamped BCS membership structure enables IT specialists to get recognition in the form of a professional title of member or fellow of the BCS - and the letters MBCS or FBCS after their name - earlier in their careers and with less bureaucracy.