In 1964 she has been engaged as research assistant and then as adjunct professor at Statistics and Demography Department in Warsaw School of Economics.
Next in 1974 she begun working in the Secretariat of the Government Council (Commission) of Demography at Planning Commission in the Council of Ministers.

In 1975–1990 she was a Scientific Secretary of Demographic Sciences Committee of Polish Academy of Sciences, and from 1995 – she became a member of Polish National Council of Statistics.

In 1986 Wasilewska-Trenkner has been appointed to a post of vice-manager in the Department of  Employment and Incomes of Population at Planning Commission in the Council of Ministers.
In 1987 she moved to a post of vice-manager in the Department of Control Systems and Methods of Planning.
She continued working there until the dissolution of Planning Commission (as an organ of Council of Ministers).
In 1989 she was invited to a post of manager of Department of Economic System in Office of Central Planning (CUP – Polish: Centralny Urząd Planowania).
Her next appointment there was a manager of CUP Department of Economic Strategy (from the beginning of 1991).
In October 1991 she has succeeded a post of Under Secretary of State in CUP.

In 1991–1992 she ran a presidency of 29th session of Senior Economic Advisers, who performed their duties at United Nations Economic Commission for Europe in Geneva, Switzerland.

From 1996 she ran a presidency of the supervisory board of Bank Gospodarstwa Krajowego (Polish National Development Bank in Warsaw).

In 1995 Wasilewska-Trenkner  was invited to Ministry of Finance.
In 1995–2001 – a post of Under Secretary of State – managing the preparation and execution of Government budget she held there.
Then – in 2001 – she became Minister of Finance, and finally – once again, in 2001–2002 – she held a post of Under Secretary of State.
In  August 2002 she became a secretary of state in Ministry of Finance responsible for Government budget.
Simultaneously – a Government Plenipotentiary to Restructuring the public finance she has been appointed.

In 2004–2010 she was a member of Monetary Policy Council (2-nd tenure).
In 2010, then president of National Bank of Poland Marek Belka invited her to perform the functions of his economic advisor.

In 2004 Wasilewska-Trenkner has been decorated with Commander (order) of Polonia Restituta.

Her death took place on 15 November 2017 in Grodzisk Mazowiecki hospital, and she was buried 22 November, in the Roman Catholic Wilanów Cemetery.
She recently lived in Owczarnia near Podkowa Leśna.

She had two children: daughter and son.

Her contribution in the range of demography, population policy and macroeconomic questions, particularly concerning dependences between demographic and economic problems is available in a number of books, papers and studies published in periodicals.
In 1964 she has been engaged as research assistant and then as adjunct professor at Statistics and Demography Department in Warsaw School of Economics. Next in 1974 she begun working in the Secretariat of the Government Council (Commission) of Demography at Planning Commission in the Council of Ministers.
In 1975–1990 she was a Scientific Secretary of Demographic Sciences Committee of Polish Academy of Sciences, and from 1995 – she became a member of Polish National Council of Statistics.
In 1986 Wasilewska-Trenkner has been appointed to a post of vice-manager in the Department of  Employment and Incomes of Population at Planning Commission in the Council of Ministers. In 1987 she moved to a post of vice-manager in the Department of Control Systems and Methods of Planning. She continued working there until the dissolution of Planning Commission (as an organ of Council of Ministers). In 1989 she was invited to a post of manager of Department of Economic System in Office of Central Planning (CUP – Polish: Centralny Urząd Planowania). Her next appointment there was a manager of CUP Department of Economic Strategy (from the beginning of 1991). In October 1991 she has succeeded a post of Under Secretary of State in CUP.
In 1991–1992 she ran a presidency of 29th session of Senior Economic Advisers, who performed their duties at United Nations Economic Commission for Europe in Geneva, Switzerland.
From 1996 she ran a presidency of the supervisory board of Bank Gospodarstwa Krajowego (Polish National Development Bank in Warsaw).
In 1995 Wasilewska-Trenkner  was invited to Ministry of Finance. In 1995–2001 – a post of Under Secretary of State – managing the preparation and execution of Government budget she held there. Then – in 2001 – she became Minister of Finance, and finally – once again, in 2001–2002 – she held a post of Under Secretary of State. In  August 2002 she became a secretary of state in Ministry of Finance responsible for Government budget. Simultaneously – a Government Plenipotentiary to Restructuring the public finance she has been appointed.
In 2004–2010 she was a member of Monetary Policy Council (2-nd tenure). In 2010, then president of National Bank of Poland Marek Belka invited her to perform the functions of his economic advisor.
In 2004 Wasilewska-Trenkner has been decorated with Commander (order) of Polonia Restituta.
Her death took place on 15 November 2017 in Grodzisk Mazowiecki hospital, and she was buried 22 November, in the Roman Catholic Wilanów Cemetery. She recently lived in Owczarnia near Podkowa Leśna.
She had two children: daughter and son.
Her contribution in the range of demography, population policy and macroeconomic questions, particularly concerning dependences between demographic and economic problems is available in a number of books, papers and studies published in periodicals.
Halina Wasilewska-Trenkner