The Regional Administrative Office of the Commonwealth Scientific and Industrial Research Organization (CSIRO) was established in Sydney in 1963. The 15th Annual Report of CSIRO states that "This Office provides accounting, staffing and purchasing services for Divisions and Sections in New South Wales and Queensland" (Parliamentary Papers, 1962-63, Vol. V, 1100). In explaining the establishment of 
a Melbourne Regional Office, the report states that  

"For many years the administration staff at Head Office in Melbourne has .... been responsible for the administrative work connected with CSIRO Divisions and Sections in Victoria, South Australia, Western Australia, Northern Territory and Tasmania. During the year under review this latter activity has been separated organisationally from the true Head Office activity as the Melbourne Regional Office..." (ibid, 969)
 
The Sydney Administrative Office, and the Canberra Administrative Office, were established at the same time. Previously they had worked as part of the State Committee (CA 2507).
 
In 1966, a separate Brisbane Regional Office was established
(CSIRO Annual Report 1965-66, p. 179), so the duties of the Sydney Office were:
 
   "This Office provides accounting, staffing and purchasing services for Divisions and Sections in New South Wales". (ibid)
 
In December 1977 the Divisions, Sections and Units of the CSIRO in New South Wales were as follows:
 
. Division of Animal Health
. Animal Health Laboratory Field Station, Badgery's Creek
. Animal Production Field Units, Armidale and Badgery's Creek 
. Animal Production Field Investigation Unit, Wollongbar
. Applied Geomechanics Field Station, Cobar
. Cloud Physics Division
. Division of Computing Research (Sydney Branch)
. Computing Research Installation, Griffith
. Cotton Research Unit, Narrabri
. Division of Entomology Laboratory
. Entomology Field Stations, Armidale, Trangie, Warrawee, Wilton 
. Ecology Units, Waste Point, Broken Hill
. Fisheries and Oceanography Division
. Food Research Division
. Genetics Research Laboratory
. Irrigation Research Division
. Land Resources Management Laboratory and Field Station, Deniliquin . Division of Mathematics and Statistics (Sydney Branch)
. Marine Biochemistry Unit
. Mineral Physics Division
. Mineral Chemistry Laboratory, Sydney
. Mineral Laboratory, Sydney
. Molecular and Cellular Biology Unit
. National Measurement Laboratory
. Australian National Radio Astronomy Observatory Office, Parkes 
. Pastoral Research Laboratory, Armidale
. Process Technology Division
. Radiophysics Division
. Textile Physics Division
. Wheat Research Unit
. Wildlife Research Laboratory, Sydney
. Wool Research Laboratories

The Regional Administrative Offices in Canberra and the state capitals were closed on 31 December 1988. Administrative Support Units were established from the previous Offices on 1 January 1989; as part of the Human Resources Branch, a component of the Corporate Services Department (started 27 February 1988).
 
Sources:
Commonwealth Government Directory, 1977, pp. 239-242
Sydney Telephone Directory, 1977, p.30
Surprise and Enterprise: Fifty Years of Science, CSIRO June 1976, addendum
CSIRO Information Services Branch, East Melbourne
 

Historical agency address
1963-1964: University Grounds, Chippendale NSW 
1964-1976: 3rd Floor, Grace Bros Building, Broadway, Sydney NSW
1976-    : Remington Centre, 175-183 Liverpool Street, Sydney NSW