Exhibit 21

Subsidiaries of the Registrant

The following are
subsidiaries of the Registrant as of December 31, 2010 and the jurisdiction in which each is organized. Each of the subsidiaries generally conducts its business using names indicated. Certain subsidiaries are not listed; these omitted
subsidiaries individually and in the aggregate do not constitute a significant subsidiary.



|                                                 |  |                                 
|------------------------------------------------ |  | --------------------------------
|Subsidiaries of Hill International, Inc.         |  | State or Country of Organization
|                                                 | 
|Transportation Construction Services, Inc.       |  | Delaware                        
|                                                 | 
|Hill International (Puerto Rico), Inc.           |  | Delaware                        
|                                                 | 
|KJM & Associates, Ltd.                           |  | Washington                      
|                                                 | 
|Stanley Baker Hill, LLC*                         |  | Delaware                        
|                                                 | 
|Hill International S.A.*                         |  | Luxembourg                      
|                                                 | 
|Hill International Development Ltd.              |  | British Virgin Islands          
|                                                 | 
|Hill International Development (II) Ltd.         |  | British Virgin Islands          
|                                                 | 
|PCI Group, LLC                                   |  | Nevada                          
|                                                 | 
|Hill International Real Estate, LLC*             |  | Pennsylvania                    
|                                                 | 
|Hill International Real Estate Partners, LP*     |  | Pennsylvania                    
|                                                 | 
|Boyken International, Inc.                       |  | Georgia                         
|                                                 | 
|TRS Consultants, Inc.                            |  | California                      
|                                                 | 
|TCM Group, Inc.                                  |  | California                      
|                                                 | 
|Subsidiaries of Hill International S.A.          |  |                                 
|                                                 | 
|Hill International (Anatolia)                    |  | Turkey                          
|                                                 | 
|SIA Hill International (Baltic)                  |  | Latvia                          
|                                                 | 
|Hill International Services Ltd.                 |  | British Virgin Islands          
|                                                 | 
|Hill International (UK) Ltd.*                    |  | England                         
|                                                 | 
|Hill International (Bucharest) S.R.L.            |  | Romania                         
|                                                 | 
|Hill International (Hellas) S.A.                 |  | Greece                          
|                                                 | 
|Hill International (Middle East) Ltd.            |  | British Virgin Islands          
|                                                 | 
|Hill Construction Management Ltd.                |  | Serbia                          
|                                                 | 
|Hill International Rijeka d.o.o.                 |  | Croatia                         
|                                                 | 
|James R. Knowles (Holdings) Ltd.*                |  | England                         
|                                                 | 
|Hill International (Libya) Ltd.                  |  | Malta                           
|                                                 | 
|Hill International (North Africa) Ltd.           |  | Egypt                           
|                                                 | 
|Asia/Pacific Hill International Holding PTE Ltd. |  | Singapore                       
|                                                 | 
|Gerens Hill International, S.A.*                 |  | Spain                           
|                                                 | 
|Hill International Sp. z o.o                     |  | Poland                          



---

|                                                  |  |          
|------------------------------------------------- |  | ---------
|                                                  | 
|Subsidiaries of Hill International (UK) Ltd.      |  |          
|                                                  | 
|Pickavance Group Ltd.                             |  | England  
|                                                  | 
|John Shreeves Holdings Ltd.*                      |  | England  
|                                                  | 
|Subsidiaries of James R. Knowles (Holdings) Ltd.  |  |          
|                                                  | 
|James R. Knowles Global Ltd.*                     |  | England  
|                                                  | 
|James R. Knowles (Worldwide) Ltd.*                |  | England  
|                                                  | 
|James R. Knowles (Australian Holdings) Pty. Ltd.* |  | Australia
|                                                  | 
|Knowles North American Holdings Inc.*             |  | Canada   
|                                                  | 
|Knowles Consultancy Services, Inc.                |  | Canada   
|                                                  | 
|Subsidiaries of Gerens Hill International, S.A.   |  |          
|                                                  | 
|Gerens Hill Gestion de Activos, S.A.              |  | Spain    
|                                                  | 
|Hill International de Mexico, S.A. de C.V.        |  | Mexico   
|                                                  | 
|Hill International Brasil Participações Ltda.     |  | Brazil   
|                                                  | 
|Subsidiary of John Shreeves Holdings Ltd.         |  |          
|                                                  | 
|John Shreeves & Partners Ltd.                     |  | England  



|* | Parent corporation of additional subsidiaries
|- | ---------------------------------------------